diff --git a/core/embed/extmod/modtrezorconfig/modtrezorconfig.c b/core/embed/extmod/modtrezorconfig/modtrezorconfig.c
index f6ffbdf15..39a2efb7e 100644
--- a/core/embed/extmod/modtrezorconfig/modtrezorconfig.c
+++ b/core/embed/extmod/modtrezorconfig/modtrezorconfig.c
@@ -36,7 +36,7 @@ STATIC mp_obj_t ui_wait_callback = mp_const_none;
 STATIC secbool wrapped_ui_wait_callback(uint32_t wait, uint32_t progress,
                                         const char *message) {
   if (mp_obj_is_callable(ui_wait_callback)) {
-    mp_obj_t args[3];
+    mp_obj_t args[3] = {0};
     args[0] = mp_obj_new_int(wait);
     args[1] = mp_obj_new_int(progress);
     args[2] = mp_obj_new_str(message, strlen(message));
@@ -74,7 +74,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorconfig_init_obj, 0, 1,
 ///     """
 STATIC mp_obj_t mod_trezorconfig_unlock(mp_obj_t pin, mp_obj_t ext_salt) {
   uint32_t pin_i = trezor_obj_get_uint(pin);
-  mp_buffer_info_t ext_salt_b;
+  mp_buffer_info_t ext_salt_b = {0};
   ext_salt_b.buf = NULL;
   if (ext_salt != mp_const_none) {
     mp_get_buffer_raise(ext_salt, &ext_salt_b, MP_BUFFER_READ);
@@ -161,7 +161,7 @@ STATIC mp_obj_t mod_trezorconfig_change_pin(size_t n_args,
                                             const mp_obj_t *args) {
   uint32_t oldpin = trezor_obj_get_uint(args[0]);
   uint32_t newpin = trezor_obj_get_uint(args[1]);
-  mp_buffer_info_t ext_salt_b;
+  mp_buffer_info_t ext_salt_b = {0};
   const uint8_t *old_ext_salt = NULL;
   if (args[2] != mp_const_none) {
     mp_get_buffer_raise(args[2], &ext_salt_b, MP_BUFFER_READ);
@@ -223,7 +223,7 @@ STATIC mp_obj_t mod_trezorconfig_change_wipe_code(size_t n_args,
                                                   const mp_obj_t *args) {
   uint32_t pin = trezor_obj_get_uint(args[0]);
   uint32_t wipe_code = trezor_obj_get_uint(args[2]);
-  mp_buffer_info_t ext_salt_b;
+  mp_buffer_info_t ext_salt_b = {0};
   const uint8_t *ext_salt = NULL;
   if (args[1] != mp_const_none) {
     mp_get_buffer_raise(args[1], &ext_salt_b, MP_BUFFER_READ);
@@ -261,7 +261,7 @@ STATIC mp_obj_t mod_trezorconfig_get(size_t n_args, const mp_obj_t *args) {
   if (len == 0) {
     return mp_const_empty_bytes;
   }
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, len);
   if (sectrue != storage_get(appkey, vstr.buf, vstr.len, &len)) {
     vstr_clear(&vstr);
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-aes.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-aes.h
index 5135ede0b..a9226bfbb 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-aes.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-aes.h
@@ -63,14 +63,14 @@ STATIC mp_obj_t mod_trezorcrypto_AES_make_new(const mp_obj_type_t *type,
   if (o->mode < ECB || o->mode > CTR) {
     mp_raise_ValueError("Invalid AES mode");
   }
-  mp_buffer_info_t key;
+  mp_buffer_info_t key = {0};
   mp_get_buffer_raise(args[1], &key, MP_BUFFER_READ);
   if (key.len != 16 && key.len != 24 && key.len != 32) {
     mp_raise_ValueError(
         "Invalid length of key (has to be 128, 192 or 256 bits)");
   }
   if (n_args > 2) {
-    mp_buffer_info_t iv;
+    mp_buffer_info_t iv = {0};
     mp_get_buffer_raise(args[2], &iv, MP_BUFFER_READ);
     if (iv.len != AES_BLOCK_SIZE) {
       mp_raise_ValueError(
@@ -98,12 +98,12 @@ STATIC mp_obj_t mod_trezorcrypto_AES_make_new(const mp_obj_type_t *type,
 }
 
 static mp_obj_t aes_update(mp_obj_t self, mp_obj_t data, bool encrypt) {
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(data, &buf, MP_BUFFER_READ);
   if (buf.len == 0) {
     return mp_const_empty_bytes;
   }
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, buf.len);
   mp_obj_AES_t *o = MP_OBJ_TO_PTR(self);
   switch (o->mode) {
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
index 3711e2209..beb91fc49 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
@@ -84,14 +84,14 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_make_new(const mp_obj_type_t *type,
        MP_ARG_KW_ONLY | MP_ARG_OBJ,
        {.u_obj = mp_const_empty_bytes}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
-  mp_buffer_info_t chain_code;
-  mp_buffer_info_t private_key;
-  mp_buffer_info_t public_key;
-  mp_buffer_info_t curve_name;
+  mp_buffer_info_t chain_code = {0};
+  mp_buffer_info_t private_key = {0};
+  mp_buffer_info_t public_key = {0};
+  mp_buffer_info_t curve_name = {0};
   const uint32_t depth = trezor_obj_get_uint(vals[0].u_obj);
   const uint32_t fingerprint = trezor_obj_get_uint(vals[1].u_obj);
   const uint32_t child_num = trezor_obj_get_uint(vals[2].u_obj);
@@ -159,7 +159,7 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_derive(size_t n_args,
   uint32_t fp = hdnode_fingerprint(&o->hdnode);
   bool public = n_args > 2 && args[2] == mp_const_true;
 
-  int res;
+  int res = 0;
   if (public) {
     res = hdnode_public_ckd(&o->hdnode, i);
   } else {
@@ -198,7 +198,7 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_derive_cardano(mp_obj_t self,
   uint32_t i = mp_obj_get_int_truncated(index);
   uint32_t fp = hdnode_fingerprint(&o->hdnode);
 
-  int res;
+  int res = 0;
   // same as in derive
   if (0 ==
       memcmp(o->hdnode.private_key,
@@ -233,8 +233,8 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_derive_path(mp_obj_t self,
   mp_obj_HDNode_t *o = MP_OBJ_TO_PTR(self);
 
   // get path objects and length
-  size_t plen;
-  mp_obj_t *pitems;
+  size_t plen = 0;
+  mp_obj_t *pitems = NULL;
   mp_obj_get_array(path, &plen, &pitems);
   if (plen > 32) {
     mp_raise_ValueError("Path cannot be longer than 32 indexes");
@@ -423,29 +423,29 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_nem_encrypt(size_t n_args,
                                                     const mp_obj_t *args) {
   mp_obj_HDNode_t *o = MP_OBJ_TO_PTR(args[0]);
 
-  mp_buffer_info_t transfer_pk;
+  mp_buffer_info_t transfer_pk = {0};
   mp_get_buffer_raise(args[1], &transfer_pk, MP_BUFFER_READ);
   if (transfer_pk.len != 32) {
     mp_raise_ValueError("transfer_public_key has invalid length");
   }
 
-  mp_buffer_info_t iv;
+  mp_buffer_info_t iv = {0};
   mp_get_buffer_raise(args[2], &iv, MP_BUFFER_READ);
   if (iv.len != 16) {
     mp_raise_ValueError("iv has invalid length");
   }
-  mp_buffer_info_t salt;
+  mp_buffer_info_t salt = {0};
   mp_get_buffer_raise(args[3], &salt, MP_BUFFER_READ);
   if (salt.len != NEM_SALT_SIZE) {
     mp_raise_ValueError("salt has invalid length");
   }
-  mp_buffer_info_t payload;
+  mp_buffer_info_t payload = {0};
   mp_get_buffer_raise(args[4], &payload, MP_BUFFER_READ);
   if (payload.len == 0) {
     mp_raise_ValueError("payload is empty");
   }
 
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, NEM_ENCRYPTED_SIZE(payload.len));
   if (!hdnode_nem_encrypt(
           &o->hdnode, *(const ed25519_public_key *)transfer_pk.buf, iv.buf,
@@ -465,7 +465,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 STATIC mp_obj_t mod_trezorcrypto_HDNode_ethereum_pubkeyhash(mp_obj_t self) {
   mp_obj_HDNode_t *o = MP_OBJ_TO_PTR(self);
 
-  uint8_t pkh[20];
+  uint8_t pkh[20] = {0};
   hdnode_get_ethereum_pubkeyhash(&o->hdnode, pkh);
   return mp_obj_new_bytes(pkh, sizeof(pkh));
 }
@@ -546,18 +546,18 @@ STATIC const mp_obj_type_t mod_trezorcrypto_HDNode_type = {
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip32_from_seed(mp_obj_t seed,
                                                  mp_obj_t curve_name) {
-  mp_buffer_info_t seedb;
+  mp_buffer_info_t seedb = {0};
   mp_get_buffer_raise(seed, &seedb, MP_BUFFER_READ);
   if (seedb.len == 0) {
     mp_raise_ValueError("Invalid seed");
   }
-  mp_buffer_info_t curveb;
+  mp_buffer_info_t curveb = {0};
   mp_get_buffer_raise(curve_name, &curveb, MP_BUFFER_READ);
   if (curveb.len == 0) {
     mp_raise_ValueError("Invalid curve name");
   }
 
-  HDNode hdnode;
+  HDNode hdnode = {0};
   int res = 0;
   if (strcmp(curveb.buf, ED25519_CARDANO_NAME) != 0) {
     res = hdnode_from_seed(seedb.buf, seedb.len, curveb.buf, &hdnode);
@@ -589,14 +589,14 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_bip32_from_seed_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip32_from_mnemonic_cardano(
     mp_obj_t mnemonic, mp_obj_t passphrase) {
-  mp_buffer_info_t mnemo, phrase;
+  mp_buffer_info_t mnemo = {0}, phrase = {0};
   mp_get_buffer_raise(mnemonic, &mnemo, MP_BUFFER_READ);
   mp_get_buffer_raise(passphrase, &phrase, MP_BUFFER_READ);
-  HDNode hdnode;
+  HDNode hdnode = {0};
   const char *pmnemonic = mnemo.len > 0 ? mnemo.buf : "";
   const char *ppassphrase = phrase.len > 0 ? phrase.buf : "";
 
-  uint8_t entropy[64];
+  uint8_t entropy[64] = {0};
   int entropy_len = mnemonic_to_entropy(pmnemonic, entropy);
 
   if (entropy_len == 0) {
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip39.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip39.h
index e65773360..adbd325a2 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip39.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip39.h
@@ -29,7 +29,7 @@
 ///     Return the first word from the wordlist starting with prefix.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip39_complete_word(mp_obj_t prefix) {
-  mp_buffer_info_t pfx;
+  mp_buffer_info_t pfx = {0};
   mp_get_buffer_raise(prefix, &pfx, MP_BUFFER_READ);
   if (pfx.len == 0) {
     return mp_const_none;
@@ -51,7 +51,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_bip39_complete_word_obj,
 ///     lowest, etc.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip39_word_completion_mask(mp_obj_t prefix) {
-  mp_buffer_info_t pfx;
+  mp_buffer_info_t pfx = {0};
   mp_get_buffer_raise(prefix, &pfx, MP_BUFFER_READ);
   return mp_obj_new_int(mnemonic_word_completion_mask(pfx.buf, pfx.len));
 }
@@ -84,7 +84,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_bip39_generate_obj,
 ///     Generate a mnemonic from given data (of 16, 20, 24, 28 and 32 bytes).
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip39_from_data(mp_obj_t data) {
-  mp_buffer_info_t bin;
+  mp_buffer_info_t bin = {0};
   mp_get_buffer_raise(data, &bin, MP_BUFFER_READ);
   if (bin.len % 4 || bin.len < 16 || bin.len > 32) {
     mp_raise_ValueError(
@@ -104,7 +104,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_bip39_from_data_obj,
 ///     Check whether given mnemonic is valid.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip39_check(mp_obj_t mnemonic) {
-  mp_buffer_info_t text;
+  mp_buffer_info_t text = {0};
   mp_get_buffer_raise(mnemonic, &text, MP_BUFFER_READ);
   return (text.len > 0 && mnemonic_check(text.buf)) ? mp_const_true
                                                     : mp_const_false;
@@ -131,11 +131,11 @@ STATIC void wrapped_ui_wait_callback(uint32_t current, uint32_t total) {
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_bip39_seed(size_t n_args,
                                             const mp_obj_t *args) {
-  mp_buffer_info_t mnemo;
-  mp_buffer_info_t phrase;
+  mp_buffer_info_t mnemo = {0};
+  mp_buffer_info_t phrase = {0};
   mp_get_buffer_raise(args[0], &mnemo, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &phrase, MP_BUFFER_READ);
-  uint8_t seed[64];
+  uint8_t seed[64] = {0};
   const char *pmnemonic = mnemo.len > 0 ? mnemo.buf : "";
   const char *ppassphrase = phrase.len > 0 ? phrase.buf : "";
   if (n_args > 2) {
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake256.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake256.h
index a5cffc18a..a254a475c 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake256.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake256.h
@@ -61,7 +61,7 @@ STATIC mp_obj_t mod_trezorcrypto_Blake256_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake256_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Blake256_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     blake256_Update(&(o->ctx), msg.buf, msg.len);
@@ -77,8 +77,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Blake256_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake256_digest(mp_obj_t self) {
   mp_obj_Blake256_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t hash[BLAKE256_DIGEST_LENGTH];
-  BLAKE256_CTX ctx;
+  uint8_t hash[BLAKE256_DIGEST_LENGTH] = {0};
+  BLAKE256_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(BLAKE256_CTX));
   blake256_Final(&ctx, hash);
   memzero(&ctx, sizeof(BLAKE256_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2b.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2b.h
index 7e05d6684..663984b04 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2b.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2b.h
@@ -64,18 +64,18 @@ STATIC mp_obj_t mod_trezorcrypto_Blake2b_make_new(const mp_obj_type_t *type,
        MP_ARG_KW_ONLY | MP_ARG_OBJ,
        {.u_obj = mp_const_empty_bytes}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
-  size_t data_len;
+  size_t data_len = 0;
   const uint8_t *data =
       (const uint8_t *)mp_obj_str_get_data(vals[0].u_obj, &data_len);
   const mp_int_t outlen = vals[1].u_int;
-  size_t key_len;
+  size_t key_len = 0;
   const uint8_t *key =
       (const uint8_t *)mp_obj_str_get_data(vals[2].u_obj, &key_len);
-  size_t personal_len;
+  size_t personal_len = 0;
   const uint8_t *personal =
       (const uint8_t *)mp_obj_str_get_data(vals[3].u_obj, &personal_len);
 
@@ -115,7 +115,7 @@ STATIC mp_obj_t mod_trezorcrypto_Blake2b_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake2b_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Blake2b_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     blake2b_Update(&(o->ctx), msg.buf, msg.len);
@@ -131,8 +131,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Blake2b_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake2b_digest(mp_obj_t self) {
   mp_obj_Blake2b_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[BLAKE2B_DIGEST_LENGTH];
-  BLAKE2B_CTX ctx;
+  uint8_t out[BLAKE2B_DIGEST_LENGTH] = {0};
+  BLAKE2B_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(BLAKE2B_CTX));
   blake2b_Final(&ctx, out, ctx.outlen);
   memzero(&ctx, sizeof(BLAKE2B_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2s.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2s.h
index 9de5d0ccc..16df666a9 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2s.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-blake2s.h
@@ -64,18 +64,18 @@ STATIC mp_obj_t mod_trezorcrypto_Blake2s_make_new(const mp_obj_type_t *type,
        MP_ARG_KW_ONLY | MP_ARG_OBJ,
        {.u_obj = mp_const_empty_bytes}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
-  size_t data_len;
+  size_t data_len = 0;
   const uint8_t *data =
       (const uint8_t *)mp_obj_str_get_data(vals[0].u_obj, &data_len);
   const mp_int_t outlen = vals[1].u_int;
-  size_t key_len;
+  size_t key_len = 0;
   const uint8_t *key =
       (const uint8_t *)mp_obj_str_get_data(vals[2].u_obj, &key_len);
-  size_t personal_len;
+  size_t personal_len = 0;
   const uint8_t *personal =
       (const uint8_t *)mp_obj_str_get_data(vals[3].u_obj, &personal_len);
 
@@ -115,7 +115,7 @@ STATIC mp_obj_t mod_trezorcrypto_Blake2s_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake2s_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Blake2s_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     blake2s_Update(&(o->ctx), msg.buf, msg.len);
@@ -131,8 +131,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Blake2s_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Blake2s_digest(mp_obj_t self) {
   mp_obj_Blake2s_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[BLAKE2S_DIGEST_LENGTH];
-  BLAKE2S_CTX ctx;
+  uint8_t out[BLAKE2S_DIGEST_LENGTH] = {0};
+  BLAKE2S_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(BLAKE2S_CTX));
   blake2s_Final(&ctx, out, ctx.outlen);
   memzero(&ctx, sizeof(BLAKE2S_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-chacha20poly1305.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-chacha20poly1305.h
index 76a964694..9937aca53 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-chacha20poly1305.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-chacha20poly1305.h
@@ -46,7 +46,7 @@ STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_make_new(
   mp_obj_ChaCha20Poly1305_t *o =
       m_new_obj_with_finaliser(mp_obj_ChaCha20Poly1305_t);
   o->base.type = type;
-  mp_buffer_info_t key, nonce;
+  mp_buffer_info_t key = {0}, nonce = {0};
   mp_get_buffer_raise(args[0], &key, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &nonce, MP_BUFFER_READ);
   if (key.len != 32) {
@@ -69,9 +69,9 @@ STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_make_new(
 STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_encrypt(mp_obj_t self,
                                                           mp_obj_t data) {
   mp_obj_ChaCha20Poly1305_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t in;
+  mp_buffer_info_t in = {0};
   mp_get_buffer_raise(data, &in, MP_BUFFER_READ);
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, in.len);
   chacha20poly1305_encrypt(&(o->ctx), in.buf, (uint8_t *)vstr.buf, in.len);
   o->plen += in.len;
@@ -88,9 +88,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_ChaCha20Poly1305_encrypt_obj,
 STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_decrypt(mp_obj_t self,
                                                           mp_obj_t data) {
   mp_obj_ChaCha20Poly1305_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t in;
+  mp_buffer_info_t in = {0};
   mp_get_buffer_raise(data, &in, MP_BUFFER_READ);
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, in.len);
   chacha20poly1305_decrypt(&(o->ctx), in.buf, (uint8_t *)vstr.buf, in.len);
   o->plen += in.len;
@@ -108,7 +108,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_ChaCha20Poly1305_decrypt_obj,
 STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_auth(mp_obj_t self,
                                                        mp_obj_t data) {
   mp_obj_ChaCha20Poly1305_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t in;
+  mp_buffer_info_t in = {0};
   mp_get_buffer_raise(data, &in, MP_BUFFER_READ);
   rfc7539_auth(&(o->ctx), in.buf, in.len);
   o->alen += in.len;
@@ -123,7 +123,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_ChaCha20Poly1305_auth_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ChaCha20Poly1305_finish(mp_obj_t self) {
   mp_obj_ChaCha20Poly1305_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[16];
+  uint8_t out[16] = {0};
   rfc7539_finish(&(o->ctx), o->alen, o->plen, out);
   return mp_obj_new_bytes(out, sizeof(out));
 }
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h
index 14f9e84f1..2cf8d7b97 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h
@@ -30,7 +30,7 @@
 ///     Computes a CRC32 checksum of `data`.
 ///     """
 mp_obj_t mod_trezorcrypto_crc_crc32(size_t n_args, const mp_obj_t *args) {
-  mp_buffer_info_t bufinfo;
+  mp_buffer_info_t bufinfo = {0};
   mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);
   uint32_t crc = (n_args > 1) ? trezor_obj_get_uint(args[1]) : 0;
   crc = checksum_crc32(bufinfo.buf, bufinfo.len, crc ^ 0xffffffff);
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-curve25519.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-curve25519.h
index 3a2d75b51..904cb4a31 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-curve25519.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-curve25519.h
@@ -30,7 +30,7 @@
 ///     Generate secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_curve25519_generate_secret() {
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   random_buffer(out, 32);
   // taken from https://cr.yp.to/ecdh.html
   out[0] &= 248;
@@ -47,12 +47,12 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(
 ///     Computes public key from secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_curve25519_publickey(mp_obj_t secret_key) {
-  mp_buffer_info_t sk;
+  mp_buffer_info_t sk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
   }
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   curve25519_scalarmult_basepoint(out, (const uint8_t *)sk.buf);
   return mp_obj_new_bytes(out, sizeof(out));
 }
@@ -66,7 +66,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_curve25519_publickey_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_curve25519_multiply(mp_obj_t secret_key,
                                                      mp_obj_t public_key) {
-  mp_buffer_info_t sk, pk;
+  mp_buffer_info_t sk = {0}, pk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   if (sk.len != 32) {
@@ -75,7 +75,7 @@ STATIC mp_obj_t mod_trezorcrypto_curve25519_multiply(mp_obj_t secret_key,
   if (pk.len != 32) {
     mp_raise_ValueError("Invalid length of public key");
   }
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   curve25519_scalarmult(out, (const uint8_t *)sk.buf, (const uint8_t *)pk.buf);
   return mp_obj_new_bytes(out, sizeof(out));
 }
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ed25519.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ed25519.h
index 81d374222..3d18162d0 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ed25519.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ed25519.h
@@ -31,7 +31,7 @@
 ///     Generate secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ed25519_generate_secret() {
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   random_buffer(out, 32);
   // taken from https://cr.yp.to/ecdh.html
   out[0] &= 248;
@@ -47,12 +47,12 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorcrypto_ed25519_generate_secret_obj,
 ///     Computes public key from secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ed25519_publickey(mp_obj_t secret_key) {
-  mp_buffer_info_t sk;
+  mp_buffer_info_t sk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
   }
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   ed25519_publickey(*(const ed25519_secret_key *)sk.buf,
                     *(ed25519_public_key *)out);
   return mp_obj_new_bytes(out, sizeof(out));
@@ -66,7 +66,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_ed25519_publickey_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ed25519_sign(size_t n_args,
                                               const mp_obj_t *args) {
-  mp_buffer_info_t sk, msg;
+  mp_buffer_info_t sk = {0}, msg = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &msg, MP_BUFFER_READ);
   if (sk.len != 32) {
@@ -75,9 +75,9 @@ STATIC mp_obj_t mod_trezorcrypto_ed25519_sign(size_t n_args,
   if (msg.len == 0) {
     mp_raise_ValueError("Empty data to sign");
   }
-  ed25519_public_key pk;
-  uint8_t out[64];
-  mp_buffer_info_t hash_func;
+  ed25519_public_key pk = {0};
+  uint8_t out[64] = {0};
+  mp_buffer_info_t hash_func = {0};
 
   if (n_args == 3) {
     mp_get_buffer_raise(args[2], &hash_func, MP_BUFFER_READ);
@@ -111,7 +111,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorcrypto_ed25519_sign_obj, 2,
 STATIC mp_obj_t mod_trezorcrypto_ed25519_sign_ext(mp_obj_t secret_key,
                                                   mp_obj_t secret_extension,
                                                   mp_obj_t message) {
-  mp_buffer_info_t sk, skext, msg;
+  mp_buffer_info_t sk = {0}, skext = {0}, msg = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(secret_extension, &skext, MP_BUFFER_READ);
   mp_get_buffer_raise(message, &msg, MP_BUFFER_READ);
@@ -124,11 +124,11 @@ STATIC mp_obj_t mod_trezorcrypto_ed25519_sign_ext(mp_obj_t secret_key,
   if (msg.len == 0) {
     mp_raise_ValueError("Empty data to sign");
   }
-  ed25519_public_key pk;
+  ed25519_public_key pk = {0};
 
   ed25519_publickey_ext(*(const ed25519_secret_key *)sk.buf,
                         *(const ed25519_secret_key *)skext.buf, pk);
-  uint8_t out[64];
+  uint8_t out[64] = {0};
   ed25519_sign_ext(msg.buf, msg.len, *(const ed25519_secret_key *)sk.buf,
                    *(const ed25519_secret_key *)skext.buf, pk,
                    *(ed25519_signature *)out);
@@ -147,7 +147,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_ed25519_sign_ext_obj,
 STATIC mp_obj_t mod_trezorcrypto_ed25519_verify(mp_obj_t public_key,
                                                 mp_obj_t signature,
                                                 mp_obj_t message) {
-  mp_buffer_info_t pk, sig, msg;
+  mp_buffer_info_t pk = {0}, sig = {0}, msg = {0};
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(message, &msg, MP_BUFFER_READ);
@@ -175,14 +175,15 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_ed25519_verify_obj,
 ///     """
 STATIC mp_obj_t
 mod_trezorcrypto_ed25519_cosi_combine_publickeys(mp_obj_t public_keys) {
-  size_t pklen;
-  mp_obj_t *pkitems;
+  size_t pklen = 0;
+  mp_obj_t *pkitems = NULL;
   mp_obj_get_array(public_keys, &pklen, &pkitems);
   if (pklen > 15) {
     mp_raise_ValueError("Can't combine more than 15 public keys");
   }
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   ed25519_public_key pks[pklen];
+  memset(pks, 0, sizeof(pks));
   for (int i = 0; i < pklen; i++) {
     mp_get_buffer_raise(pkitems[i], &buf, MP_BUFFER_READ);
     if (buf.len != 32) {
@@ -190,7 +191,7 @@ mod_trezorcrypto_ed25519_cosi_combine_publickeys(mp_obj_t public_keys) {
     }
     memcpy(pks[i], buf.buf, buf.len);
   }
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   if (0 !=
       ed25519_cosi_combine_publickeys(*(ed25519_public_key *)out, pks, pklen)) {
     mp_raise_ValueError("Error combining public keys");
@@ -207,19 +208,20 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ed25519_cosi_combine_signatures(
     mp_obj_t R, mp_obj_t signatures) {
-  mp_buffer_info_t sigR;
+  mp_buffer_info_t sigR = {0};
   mp_get_buffer_raise(R, &sigR, MP_BUFFER_READ);
   if (sigR.len != 32) {
     mp_raise_ValueError("Invalid length of R");
   }
-  size_t siglen;
-  mp_obj_t *sigitems;
+  size_t siglen = 0;
+  mp_obj_t *sigitems = NULL;
   mp_obj_get_array(signatures, &siglen, &sigitems);
   if (siglen > 15) {
     mp_raise_ValueError("Can't combine more than 15 COSI signatures");
   }
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   ed25519_cosi_signature sigs[siglen];
+  memset(sigs, 0, sizeof(sigs));
   for (int i = 0; i < siglen; i++) {
     mp_get_buffer_raise(sigitems[i], &buf, MP_BUFFER_READ);
     if (buf.len != 32) {
@@ -227,7 +229,7 @@ STATIC mp_obj_t mod_trezorcrypto_ed25519_cosi_combine_signatures(
     }
     memcpy(sigs[i], buf.buf, buf.len);
   }
-  uint8_t out[64];
+  uint8_t out[64] = {0};
   ed25519_cosi_combine_signatures(*(ed25519_signature *)out,
                                   *(const ed25519_public_key *)sigR.buf, sigs,
                                   siglen);
@@ -249,7 +251,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ed25519_cosi_sign(size_t n_args,
                                                    const mp_obj_t *args) {
-  mp_buffer_info_t sk, msg, nonce, sigR, pk;
+  mp_buffer_info_t sk = {0}, msg = {0}, nonce = {0}, sigR = {0}, pk = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &msg, MP_BUFFER_READ);
   mp_get_buffer_raise(args[2], &nonce, MP_BUFFER_READ);
@@ -267,7 +269,7 @@ STATIC mp_obj_t mod_trezorcrypto_ed25519_cosi_sign(size_t n_args,
   if (pk.len != 32) {
     mp_raise_ValueError("Invalid length of aggregated public key");
   }
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   ed25519_cosi_sign(msg.buf, msg.len, *(const ed25519_secret_key *)sk.buf,
                     *(const ed25519_secret_key *)nonce.buf,
                     *(const ed25519_public_key *)sigR.buf,
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-groestl.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-groestl.h
index 51fd76c2d..891fdc8f6 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-groestl.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-groestl.h
@@ -65,7 +65,7 @@ STATIC mp_obj_t mod_trezorcrypto_Groestl512_make_new(const mp_obj_type_t *type,
 STATIC mp_obj_t mod_trezorcrypto_Groestl512_update(mp_obj_t self,
                                                    mp_obj_t data) {
   mp_obj_Groestl512_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     groestl512_Update(&(o->ctx), msg.buf, msg.len);
@@ -81,8 +81,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Groestl512_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Groestl512_digest(mp_obj_t self) {
   mp_obj_Groestl512_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[GROESTL512_DIGEST_LENGTH];
-  GROESTL512_CTX ctx;
+  uint8_t out[GROESTL512_DIGEST_LENGTH] = {0};
+  GROESTL512_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(GROESTL512_CTX));
   groestl512_Final(&ctx, out);
   memzero(&ctx, sizeof(GROESTL512_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-monero.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-monero.h
index 939f6a4ab..922a4ed02 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-monero.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-monero.h
@@ -83,7 +83,7 @@ static uint64_t mp_obj_uint64_get_checked(mp_const_obj_t self_in) {
   if (MP_OBJ_IS_SMALL_INT(self_in)) {
     return MP_OBJ_SMALL_INT_VALUE(self_in);
   } else {
-    byte buff[8];
+    byte buff[8] = {0};
     uint64_t res = 0;
     mp_obj_t *o = MP_OBJ_TO_PTR(self_in);
 
@@ -149,7 +149,7 @@ STATIC mp_obj_t mp_obj_new_ge25519_r(mp_obj_t r) {
 }
 
 STATIC void mp_unpack_ge25519(ge25519 *r, const mp_obj_t arg, mp_int_t offset) {
-  mp_buffer_info_t buff;
+  mp_buffer_info_t buff = {0};
   mp_get_buffer_raise(arg, &buff, MP_BUFFER_READ);
   if (buff.len < 32 + offset) {
     mp_raise_ValueError("Invalid length of the EC point");
@@ -163,7 +163,7 @@ STATIC void mp_unpack_ge25519(ge25519 *r, const mp_obj_t arg, mp_int_t offset) {
 
 STATIC void mp_unpack_scalar(bignum256modm r, const mp_obj_t arg,
                              mp_int_t offset) {
-  mp_buffer_info_t buff;
+  mp_buffer_info_t buff = {0};
   mp_get_buffer_raise(arg, &buff, MP_BUFFER_READ);
   if (buff.len < 32 + offset) {
     mp_raise_ValueError("Invalid length of secret key");
@@ -291,7 +291,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_hasher_make_new(
   xmr_hasher_init(&(o->h));
 
   if (n_args == 1 && MP_OBJ_IS_STR_OR_BYTES(args[0])) {
-    mp_buffer_info_t buff;
+    mp_buffer_info_t buff = {0};
     mp_get_buffer_raise(args[0], &buff, MP_BUFFER_READ);
     xmr_hasher_update(&o->h, buff.buf, buff.len);
   }
@@ -390,7 +390,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_monero_eq256_modm_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_monero_get256_modm(const mp_obj_t arg) {
   assert_scalar(arg);
-  uint64_t v;
+  uint64_t v = 0;
   if (!get256_modm(&v, MP_OBJ_C_SCALAR(arg))) {
     mp_raise_ValueError("Ed25519 scalar too big");
   }
@@ -521,9 +521,9 @@ STATIC mp_obj_t mod_trezorcrypto_monero_inv256_modm(size_t n_args,
   // bn_prime = curve order, little endian encoded
   bignum256 bn_prime = {.val = {0x1cf5d3ed, 0x9318d2, 0x1de73596, 0x1df3bd45,
                                 0x14d, 0x0, 0x0, 0x0, 0x100000}};
-  bignum256 bn_x;
-  bignum256modm bm_x;
-  uint8_t raw_x[32];
+  bignum256 bn_x = {0};
+  bignum256modm bm_x = {0};
+  uint8_t raw_x[32] = {0};
 
   memcpy(bm_x, MP_OBJ_C_SCALAR(args[1 + off]), sizeof(bignum256modm));
   contract256_modm(raw_x, bm_x);
@@ -551,12 +551,12 @@ STATIC mp_obj_t mod_trezorcrypto_monero_pack256_modm(size_t n_args,
                                                      const mp_obj_t *args) {
   if (n_args == 1 || args[0] == mp_const_none) {
     assert_scalar(args[0]);
-    uint8_t buff[32];
+    uint8_t buff[32] = {0};
     contract256_modm(buff, MP_OBJ_C_SCALAR(args[0]));
     return mp_obj_new_bytes(buff, 32);
 
   } else {
-    mp_buffer_info_t bufm;
+    mp_buffer_info_t bufm = {0};
     mp_get_buffer_raise(args[0], &bufm, MP_BUFFER_WRITE);
     const mp_int_t offset = n_args >= 3 ? mp_obj_get_int(args[2]) : 0;
     if (bufm.len < 32 + offset) {
@@ -603,7 +603,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_unpack256_modm_noreduce(
   mp_obj_t res = mp_obj_new_scalar_r(res_arg ? args[0] : mp_const_none);
   const mp_int_t offset = n_args >= 3 ? mp_obj_get_int(args[2]) : 0;
 
-  mp_buffer_info_t buff;
+  mp_buffer_info_t buff = {0};
   mp_get_buffer_raise(args[1 + off], &buff, MP_BUFFER_READ);
   if (buff.len != 32 + offset) {
     mp_raise_ValueError("Invalid length of secret key");
@@ -821,7 +821,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_ge25519_scalarmult_base(
     ge25519_scalarmult_base_wrapper(&MP_OBJ_GE25519(res),
                                     MP_OBJ_C_SCALAR(args[1 + off]));
   } else if (mp_obj_is_integer(args[1 + off])) {
-    bignum256modm mlt;
+    bignum256modm mlt = {0};
     set256_modm(mlt, mp_obj_get_int(args[1 + off]));
     ge25519_scalarmult_base_wrapper(&MP_OBJ_GE25519(res), mlt);
   } else {
@@ -851,7 +851,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_ge25519_scalarmult(
     ge25519_scalarmult(&MP_OBJ_GE25519(res), &MP_OBJ_C_GE25519(args[1 + off]),
                        MP_OBJ_C_SCALAR(args[2 + off]));
   } else if (mp_obj_is_integer(args[2 + off])) {
-    bignum256modm mlt;
+    bignum256modm mlt = {0};
     set256_modm(mlt, mp_obj_get_int(args[2 + off]));
     ge25519_scalarmult(&MP_OBJ_GE25519(res), &MP_OBJ_C_GE25519(args[1 + off]),
                        mlt);
@@ -873,12 +873,12 @@ STATIC mp_obj_t mod_trezorcrypto_monero_ge25519_pack(size_t n_args,
                                                      const mp_obj_t *args) {
   if (n_args == 1 || args[0] == mp_const_none) {
     assert_ge25519(args[0]);
-    uint8_t buff[32];
+    uint8_t buff[32] = {0};
     ge25519_pack(buff, &MP_OBJ_C_GE25519(args[0]));
     return mp_obj_new_bytes(buff, 32);
 
   } else {
-    mp_buffer_info_t bufm;
+    mp_buffer_info_t bufm = {0};
     mp_get_buffer_raise(args[0], &bufm, MP_BUFFER_WRITE);
     const mp_int_t offset = n_args >= 3 ? mp_obj_get_int(args[2]) : 0;
     if (bufm.len < 32 + offset) {
@@ -922,8 +922,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_monero_xmr_base58_addr_encode_check(
     size_t n_args, const mp_obj_t *args) {
-  uint8_t out[128];
-  mp_buffer_info_t data;
+  uint8_t out[128] = {0};
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[1], &data, MP_BUFFER_READ);
 
   int sz = xmr_base58_addr_encode_check(mp_obj_get_int(args[0]), data.buf,
@@ -945,10 +945,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_monero_xmr_base58_addr_decode_check(
     size_t n_args, const mp_obj_t *args) {
-  uint8_t out[128];
-  uint64_t tag;
+  uint8_t out[128] = {0};
+  uint64_t tag = 0;
 
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[0], &data, MP_BUFFER_READ);
 
   int sz =
@@ -989,10 +989,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 STATIC mp_obj_t mod_trezorcrypto_monero_xmr_fast_hash(size_t n_args,
                                                       const mp_obj_t *args) {
   const int off = n_args >= 2 ? 0 : -1;
-  uint8_t buff[32];
+  uint8_t buff[32] = {0};
   uint8_t *buff_use = buff;
   if (n_args > 1) {
-    mp_buffer_info_t odata;
+    mp_buffer_info_t odata = {0};
     mp_get_buffer_raise(args[0], &odata, MP_BUFFER_WRITE);
     if (odata.len < 32) {
       mp_raise_ValueError("Output buffer too small");
@@ -1000,7 +1000,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_xmr_fast_hash(size_t n_args,
     buff_use = odata.buf;
   }
 
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[1 + off], &data, MP_BUFFER_READ);
   mp_int_t length = n_args >= 3 ? mp_obj_get_int(args[2]) : data.len;
   mp_int_t offset = n_args >= 4 ? mp_obj_get_int(args[3]) : 0;
@@ -1028,7 +1028,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_xmr_hash_to_ec(size_t n_args,
   const bool res_arg = n_args >= 2;
   const int off = res_arg ? 0 : -1;
   mp_obj_t res = mp_obj_new_ge25519_r(res_arg ? args[0] : mp_const_none);
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[1 + off], &data, MP_BUFFER_READ);
   mp_int_t length = n_args >= 3 ? mp_obj_get_int(args[2]) : data.len;
   mp_int_t offset = n_args >= 4 ? mp_obj_get_int(args[3]) : 0;
@@ -1057,7 +1057,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_xmr_hash_to_scalar(
   const bool res_arg = n_args >= 2;
   const int off = res_arg ? 0 : -1;
   mp_obj_t res = mp_obj_new_scalar_r(res_arg ? args[0] : mp_const_none);
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[1 + off], &data, MP_BUFFER_READ);
   mp_int_t length = n_args >= 3 ? mp_obj_get_int(args[2]) : data.len;
   mp_int_t offset = n_args >= 4 ? mp_obj_get_int(args[3]) : 0;
@@ -1298,7 +1298,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 ///     Constant time buffer comparison
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_ct_equals(const mp_obj_t a, const mp_obj_t b) {
-  mp_buffer_info_t buff_a, buff_b;
+  mp_buffer_info_t buff_a = {0}, buff_b = {0};
   mp_get_buffer_raise(a, &buff_a, MP_BUFFER_READ);
   mp_get_buffer_raise(b, &buff_b, MP_BUFFER_READ);
 
@@ -1316,7 +1316,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_ct_equals_obj,
 STATIC mp_obj_t mod_trezorcrypto_monero_hasher_update(mp_obj_t self,
                                                       const mp_obj_t arg) {
   mp_obj_hasher_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buff;
+  mp_buffer_info_t buff = {0};
   mp_get_buffer_raise(arg, &buff, MP_BUFFER_READ);
   if (buff.len > 0) {
     xmr_hasher_update(&o->h, buff.buf, buff.len);
@@ -1330,10 +1330,10 @@ STATIC mp_obj_t mod_trezorcrypto_monero_hasher_digest(size_t n_args,
                                                       const mp_obj_t *args) {
   mp_obj_hasher_t *o = MP_OBJ_TO_PTR(args[0]);
 
-  Hasher ctx;
+  Hasher ctx = {0};
   memcpy(&ctx, &(o->h), sizeof(Hasher));
 
-  uint8_t out[SHA3_256_DIGEST_LENGTH];
+  uint8_t out[SHA3_256_DIGEST_LENGTH] = {0};
   xmr_hasher_final(&ctx, out);
   memzero(&ctx, sizeof(SHA3_CTX));
 
@@ -1341,7 +1341,7 @@ STATIC mp_obj_t mod_trezorcrypto_monero_hasher_digest(size_t n_args,
     return mp_obj_new_bytes(out, sizeof(out));
 
   } else {
-    mp_buffer_info_t bufm;
+    mp_buffer_info_t bufm = {0};
     mp_get_buffer_raise(args[1], &bufm, MP_BUFFER_WRITE);
     const mp_int_t offset = n_args >= 3 ? mp_obj_get_int(args[2]) : 0;
     if (bufm.len < 32 + offset) {
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nem.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nem.h
index 3fa67e68b..5658954d2 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nem.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nem.h
@@ -31,7 +31,7 @@
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nem_validate_address(mp_obj_t address,
                                                       mp_obj_t network) {
-  mp_buffer_info_t addr;
+  mp_buffer_info_t addr = {0};
   mp_get_buffer_raise(address, &addr, MP_BUFFER_READ);
 
   uint32_t n = trezor_obj_get_uint(network);
@@ -46,7 +46,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_nem_validate_address_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nem_compute_address(mp_obj_t public_key,
                                                      mp_obj_t network) {
-  mp_buffer_info_t p;
+  mp_buffer_info_t p = {0};
   mp_get_buffer_raise(public_key, &p, MP_BUFFER_READ);
 
   uint32_t n = trezor_obj_get_uint(network);
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nist256p1.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nist256p1.h
index a874f1ff4..0f55a4d64 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nist256p1.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-nist256p1.h
@@ -29,7 +29,7 @@
 ///     Generate secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_generate_secret() {
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   for (;;) {
     random_buffer(out, 32);
     // check whether secret > 0 && secret < curve_order
@@ -60,18 +60,18 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorcrypto_nist256p1_generate_secret_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_publickey(size_t n_args,
                                                      const mp_obj_t *args) {
-  mp_buffer_info_t sk;
+  mp_buffer_info_t sk = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
   }
   bool compressed = n_args < 2 || args[1] == mp_const_true;
   if (compressed) {
-    uint8_t out[33];
+    uint8_t out[33] = {0};
     ecdsa_get_public_key33(&nist256p1, (const uint8_t *)sk.buf, out);
     return mp_obj_new_bytes(out, sizeof(out));
   } else {
-    uint8_t out[65];
+    uint8_t out[65] = {0};
     ecdsa_get_public_key65(&nist256p1, (const uint8_t *)sk.buf, out);
     return mp_obj_new_bytes(out, sizeof(out));
   }
@@ -88,7 +88,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_sign(size_t n_args,
                                                 const mp_obj_t *args) {
-  mp_buffer_info_t sk, dig;
+  mp_buffer_info_t sk = {0}, dig = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &dig, MP_BUFFER_READ);
   bool compressed = n_args < 3 || args[2] == mp_const_true;
@@ -98,7 +98,7 @@ STATIC mp_obj_t mod_trezorcrypto_nist256p1_sign(size_t n_args,
   if (dig.len != 32) {
     mp_raise_ValueError("Invalid length of digest");
   }
-  uint8_t out[65], pby;
+  uint8_t out[65] = {0}, pby = 0;
   if (0 != ecdsa_sign_digest(&nist256p1, (const uint8_t *)sk.buf,
                              (const uint8_t *)dig.buf, out + 1, &pby, NULL)) {
     mp_raise_ValueError("Signing failed");
@@ -118,7 +118,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorcrypto_nist256p1_sign_obj,
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_verify(mp_obj_t public_key,
                                                   mp_obj_t signature,
                                                   mp_obj_t digest) {
-  mp_buffer_info_t pk, sig, dig;
+  mp_buffer_info_t pk = {0}, sig = {0}, dig = {0};
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
@@ -147,7 +147,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_nist256p1_verify_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_verify_recover(mp_obj_t signature,
                                                           mp_obj_t digest) {
-  mp_buffer_info_t sig, dig;
+  mp_buffer_info_t sig = {0}, dig = {0};
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
   if (sig.len != 65) {
@@ -162,7 +162,7 @@ STATIC mp_obj_t mod_trezorcrypto_nist256p1_verify_recover(mp_obj_t signature,
   }
   bool compressed = (recid >= 4);
   recid &= 3;
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   if (0 == ecdsa_recover_pub_from_sig(&nist256p1, out,
                                       (const uint8_t *)sig.buf + 1,
                                       (const uint8_t *)dig.buf, recid)) {
@@ -185,7 +185,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_nist256p1_verify_recover_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_nist256p1_multiply(mp_obj_t secret_key,
                                                     mp_obj_t public_key) {
-  mp_buffer_info_t sk, pk;
+  mp_buffer_info_t sk = {0}, pk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   if (sk.len != 32) {
@@ -194,7 +194,7 @@ STATIC mp_obj_t mod_trezorcrypto_nist256p1_multiply(mp_obj_t secret_key,
   if (pk.len != 33 && pk.len != 65) {
     mp_raise_ValueError("Invalid length of public key");
   }
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   if (0 != ecdh_multiply(&nist256p1, (const uint8_t *)sk.buf,
                          (const uint8_t *)pk.buf, out)) {
     mp_raise_ValueError("Multiply failed");
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-pbkdf2.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-pbkdf2.h
index 2028672d9..ada3a7919 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-pbkdf2.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-pbkdf2.h
@@ -62,9 +62,9 @@ STATIC mp_obj_t mod_trezorcrypto_Pbkdf2_make_new(const mp_obj_type_t *type,
   mp_obj_Pbkdf2_t *o = m_new_obj_with_finaliser(mp_obj_Pbkdf2_t);
   o->base.type = type;
 
-  mp_buffer_info_t password;
+  mp_buffer_info_t password = {0};
   mp_get_buffer_raise(args[1], &password, MP_BUFFER_READ);
-  mp_buffer_info_t salt;
+  mp_buffer_info_t salt = {0};
   mp_get_buffer_raise(args[2], &salt, MP_BUFFER_READ);
 
   if (password.len == 0) {
@@ -122,17 +122,17 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Pbkdf2_update_obj,
 STATIC mp_obj_t mod_trezorcrypto_Pbkdf2_key(mp_obj_t self) {
   mp_obj_Pbkdf2_t *o = MP_OBJ_TO_PTR(self);
   if (o->prf == PRF_HMAC_SHA256) {
-    PBKDF2_HMAC_SHA256_CTX ctx;
+    PBKDF2_HMAC_SHA256_CTX ctx = {0};
     memcpy(&ctx, &(o->ctx256), sizeof(PBKDF2_HMAC_SHA256_CTX));
-    uint8_t out[SHA256_DIGEST_LENGTH];
+    uint8_t out[SHA256_DIGEST_LENGTH] = {0};
     pbkdf2_hmac_sha256_Final(&ctx, out);
     memzero(&ctx, sizeof(PBKDF2_HMAC_SHA256_CTX));
     return mp_obj_new_bytes(out, sizeof(out));
   }
   if (o->prf == PRF_HMAC_SHA512) {
-    PBKDF2_HMAC_SHA512_CTX ctx;
+    PBKDF2_HMAC_SHA512_CTX ctx = {0};
     memcpy(&ctx, &(o->ctx512), sizeof(PBKDF2_HMAC_SHA512_CTX));
-    uint8_t out[SHA512_DIGEST_LENGTH];
+    uint8_t out[SHA512_DIGEST_LENGTH] = {0};
     pbkdf2_hmac_sha512_Final(&ctx, out);
     memzero(&ctx, sizeof(PBKDF2_HMAC_SHA512_CTX));
     return mp_obj_new_bytes(out, sizeof(out));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-random.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-random.h
index d67a3ae4a..61030ffc4 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-random.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-random.h
@@ -49,7 +49,7 @@ STATIC mp_obj_t mod_trezorcrypto_random_bytes(mp_obj_t len) {
   if (l > 1024) {
     mp_raise_ValueError("Maximum requested size is 1024");
   }
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, l);
   random_buffer((uint8_t *)vstr.buf, l);
   return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
@@ -62,8 +62,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_random_bytes_obj,
 ///     Shuffles items of given list (in-place).
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_random_shuffle(mp_obj_t data) {
-  size_t count;
-  mp_obj_t *items;
+  size_t count = 0;
+  mp_obj_t *items = NULL;
   mp_obj_get_array(data, &count, &items);
   if (count > 256) {
     mp_raise_ValueError("Maximum list size is 256 items");
@@ -72,7 +72,7 @@ STATIC mp_obj_t mod_trezorcrypto_random_shuffle(mp_obj_t data) {
     return mp_const_none;
   }
   // Fisher-Yates shuffle
-  mp_obj_t t;
+  mp_obj_t t = 0;
   for (size_t i = count - 1; i >= 1; i--) {
     size_t j = random_uniform(i + 1);
     t = items[i];
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ripemd160.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ripemd160.h
index 64416ea23..12f3d05df 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ripemd160.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-ripemd160.h
@@ -62,7 +62,7 @@ STATIC mp_obj_t mod_trezorcrypto_Ripemd160_make_new(const mp_obj_type_t *type,
 STATIC mp_obj_t mod_trezorcrypto_Ripemd160_update(mp_obj_t self,
                                                   mp_obj_t data) {
   mp_obj_Ripemd160_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     ripemd160_Update(&(o->ctx), msg.buf, msg.len);
@@ -78,8 +78,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Ripemd160_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Ripemd160_digest(mp_obj_t self) {
   mp_obj_Ripemd160_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[RIPEMD160_DIGEST_LENGTH];
-  RIPEMD160_CTX ctx;
+  uint8_t out[RIPEMD160_DIGEST_LENGTH] = {0};
+  RIPEMD160_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(RIPEMD160_CTX));
   ripemd160_Final(&ctx, out);
   memzero(&ctx, sizeof(RIPEMD160_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1.h
index 0d250be31..4d87c9478 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1.h
@@ -29,7 +29,7 @@
 ///     Generate secret key.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_generate_secret() {
-  uint8_t out[32];
+  uint8_t out[32] = {0};
   for (;;) {
     random_buffer(out, 32);
     // check whether secret > 0 && secret < curve_order
@@ -60,18 +60,18 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorcrypto_secp256k1_generate_secret_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_publickey(size_t n_args,
                                                      const mp_obj_t *args) {
-  mp_buffer_info_t sk;
+  mp_buffer_info_t sk = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
   }
   bool compressed = n_args < 2 || args[1] == mp_const_true;
   if (compressed) {
-    uint8_t out[33];
+    uint8_t out[33] = {0};
     ecdsa_get_public_key33(&secp256k1, (const uint8_t *)sk.buf, out);
     return mp_obj_new_bytes(out, sizeof(out));
   } else {
-    uint8_t out[65];
+    uint8_t out[65] = {0};
     ecdsa_get_public_key65(&secp256k1, (const uint8_t *)sk.buf, out);
     return mp_obj_new_bytes(out, sizeof(out));
   }
@@ -117,7 +117,7 @@ enum {
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_sign(size_t n_args,
                                                 const mp_obj_t *args) {
-  mp_buffer_info_t sk, dig;
+  mp_buffer_info_t sk = {0}, dig = {0};
   mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[1], &dig, MP_BUFFER_READ);
   bool compressed = (n_args < 3) || (args[2] == mp_const_true);
@@ -139,7 +139,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_sign(size_t n_args,
   if (dig.len != 32) {
     mp_raise_ValueError("Invalid length of digest");
   }
-  uint8_t out[65], pby;
+  uint8_t out[65] = {0}, pby = 0;
   if (0 != ecdsa_sign_digest(&secp256k1, (const uint8_t *)sk.buf,
                              (const uint8_t *)dig.buf, out + 1, &pby,
                              is_canonical)) {
@@ -160,7 +160,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorcrypto_secp256k1_sign_obj,
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_verify(mp_obj_t public_key,
                                                   mp_obj_t signature,
                                                   mp_obj_t digest) {
-  mp_buffer_info_t pk, sig, dig;
+  mp_buffer_info_t pk = {0}, sig = {0}, dig = {0};
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
@@ -189,7 +189,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_secp256k1_verify_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_verify_recover(mp_obj_t signature,
                                                           mp_obj_t digest) {
-  mp_buffer_info_t sig, dig;
+  mp_buffer_info_t sig = {0}, dig = {0};
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
   if (sig.len != 65) {
@@ -204,7 +204,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_verify_recover(mp_obj_t signature,
   }
   bool compressed = (recid >= 4);
   recid &= 3;
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   if (0 == ecdsa_recover_pub_from_sig(&secp256k1, out,
                                       (const uint8_t *)sig.buf + 1,
                                       (const uint8_t *)dig.buf, recid)) {
@@ -227,7 +227,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_secp256k1_verify_recover_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_multiply(mp_obj_t secret_key,
                                                     mp_obj_t public_key) {
-  mp_buffer_info_t sk, pk;
+  mp_buffer_info_t sk = {0}, pk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   if (sk.len != 32) {
@@ -236,7 +236,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_multiply(mp_obj_t secret_key,
   if (pk.len != 33 && pk.len != 65) {
     mp_raise_ValueError("Invalid length of public key");
   }
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   if (0 != ecdh_multiply(&secp256k1, (const uint8_t *)sk.buf,
                          (const uint8_t *)pk.buf, out)) {
     mp_raise_ValueError("Multiply failed");
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
index 02c4d366b..8477b43f6 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
@@ -152,7 +152,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_publickey(
     size_t n_args, const mp_obj_t *args) {
   const secp256k1_context *ctx =
       mod_trezorcrypto_get_secp256k1_context(args[0]);
-  mp_buffer_info_t sk;
+  mp_buffer_info_t sk = {0};
   mp_get_buffer_raise(args[1], &sk, MP_BUFFER_READ);
   secp256k1_pubkey pk;
   if (sk.len != 32) {
@@ -163,7 +163,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_publickey(
   }
 
   bool compressed = n_args < 3 || args[2] == mp_const_true;
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   size_t outlen = sizeof(out);
   secp256k1_ec_pubkey_serialize(
       ctx, out, &outlen, &pk,
@@ -184,7 +184,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_sign(size_t n_args,
                                                         const mp_obj_t *args) {
   const secp256k1_context *ctx =
       mod_trezorcrypto_get_secp256k1_context(args[0]);
-  mp_buffer_info_t sk, dig;
+  mp_buffer_info_t sk = {0}, dig = {0};
   mp_get_buffer_raise(args[1], &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[2], &dig, MP_BUFFER_READ);
   bool compressed = n_args < 4 || args[3] == mp_const_true;
@@ -195,8 +195,8 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_sign(size_t n_args,
     mp_raise_ValueError("Invalid length of digest");
   }
   secp256k1_ecdsa_recoverable_signature sig;
-  uint8_t out[65];
-  int pby;
+  uint8_t out[65] = {0};
+  int pby = 0;
   if (!secp256k1_ecdsa_sign_recoverable(ctx, &sig, (const uint8_t *)dig.buf,
                                         (const uint8_t *)sk.buf, NULL, NULL)) {
     mp_raise_ValueError("Signing failed");
@@ -221,7 +221,7 @@ STATIC mp_obj_t
 mod_trezorcrypto_secp256k1_context_verify(size_t n_args, const mp_obj_t *args) {
   const secp256k1_context *ctx =
       mod_trezorcrypto_get_secp256k1_context(args[0]);
-  mp_buffer_info_t pk, sig, dig;
+  mp_buffer_info_t pk = {0}, sig = {0}, dig = {0};
   mp_get_buffer_raise(args[1], &pk, MP_BUFFER_READ);
   mp_get_buffer_raise(args[2], &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(args[3], &dig, MP_BUFFER_READ);
@@ -261,7 +261,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_verify_recover(
     mp_obj_t self, mp_obj_t signature, mp_obj_t digest) {
   const secp256k1_context *ctx = mod_trezorcrypto_get_secp256k1_context(self);
-  mp_buffer_info_t sig, dig;
+  mp_buffer_info_t sig = {0}, dig = {0};
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
   if (sig.len != 65) {
@@ -286,7 +286,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_verify_recover(
   if (!secp256k1_ecdsa_recover(ctx, &pk, &ec_sig, (const uint8_t *)dig.buf)) {
     return mp_const_none;
   }
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   size_t pklen = sizeof(out);
   secp256k1_ec_pubkey_serialize(
       ctx, out, &pklen, &pk,
@@ -314,7 +314,7 @@ static int secp256k1_ecdh_hash_passthrough(uint8_t *output, const uint8_t *x,
 STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_multiply(
     mp_obj_t self, mp_obj_t secret_key, mp_obj_t public_key) {
   const secp256k1_context *ctx = mod_trezorcrypto_get_secp256k1_context(self);
-  mp_buffer_info_t sk, pk;
+  mp_buffer_info_t sk = {0}, pk = {0};
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
   if (sk.len != 32) {
@@ -328,7 +328,7 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_multiply(
                                  pk.len)) {
     mp_raise_ValueError("Invalid public key");
   }
-  uint8_t out[65];
+  uint8_t out[65] = {0};
   if (!secp256k1_ecdh(ctx, out, &ec_pk, (const uint8_t *)sk.buf,
                       secp256k1_ecdh_hash_passthrough, NULL)) {
     mp_raise_ValueError("Multiply failed");
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha1.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha1.h
index d69f78f9f..ed793f354 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha1.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha1.h
@@ -61,7 +61,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha1_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha1_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Sha1_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     sha1_Update(&(o->ctx), msg.buf, msg.len);
@@ -77,8 +77,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Sha1_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha1_digest(mp_obj_t self) {
   mp_obj_Sha1_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[SHA1_DIGEST_LENGTH];
-  SHA1_CTX ctx;
+  uint8_t out[SHA1_DIGEST_LENGTH] = {0};
+  SHA1_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(SHA1_CTX));
   sha1_Final(&ctx, out);
   memzero(&ctx, sizeof(SHA1_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha256.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha256.h
index 4e9e11e19..9baac59f5 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha256.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha256.h
@@ -61,7 +61,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha256_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha256_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Sha256_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     sha256_Update(&(o->ctx), msg.buf, msg.len);
@@ -77,8 +77,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Sha256_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha256_digest(mp_obj_t self) {
   mp_obj_Sha256_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[SHA256_DIGEST_LENGTH];
-  SHA256_CTX ctx;
+  uint8_t out[SHA256_DIGEST_LENGTH] = {0};
+  SHA256_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(SHA256_CTX));
   sha256_Final(&ctx, out);
   memzero(&ctx, sizeof(SHA256_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-256.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-256.h
index e7c787eb9..880b40adc 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-256.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-256.h
@@ -55,7 +55,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha3_256_make_new(const mp_obj_type_t *type,
       {MP_QSTR_data, MP_ARG_OBJ, {.u_obj = mp_const_none}},
       {MP_QSTR_keccak, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_OBJ_NULL}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
   if (vals[1].u_obj != MP_OBJ_NULL) {
@@ -74,7 +74,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha3_256_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha3_256_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Sha3_256_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     sha3_Update(&(o->ctx), msg.buf, msg.len);
@@ -90,8 +90,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Sha3_256_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha3_256_digest(mp_obj_t self) {
   mp_obj_Sha3_256_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[SHA3_256_DIGEST_LENGTH];
-  SHA3_CTX ctx;
+  uint8_t out[SHA3_256_DIGEST_LENGTH] = {0};
+  SHA3_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(SHA3_CTX));
   if (o->keccak) {
     keccak_Final(&ctx, out);
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-512.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-512.h
index 0505cde98..91200f2cf 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-512.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha3-512.h
@@ -55,7 +55,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha3_512_make_new(const mp_obj_type_t *type,
       {MP_QSTR_data, MP_ARG_OBJ, {.u_obj = mp_const_none}},
       {MP_QSTR_keccak, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_OBJ_NULL}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
   if (vals[1].u_obj != MP_OBJ_NULL) {
@@ -74,7 +74,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha3_512_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha3_512_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Sha3_512_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     sha3_Update(&(o->ctx), msg.buf, msg.len);
@@ -90,8 +90,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Sha3_512_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha3_512_digest(mp_obj_t self) {
   mp_obj_Sha3_512_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[SHA3_512_DIGEST_LENGTH];
-  SHA3_CTX ctx;
+  uint8_t out[SHA3_512_DIGEST_LENGTH] = {0};
+  SHA3_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(SHA3_CTX));
   if (o->keccak) {
     keccak_Final(&ctx, out);
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha512.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha512.h
index 46d33379c..983060b64 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha512.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-sha512.h
@@ -60,7 +60,7 @@ STATIC mp_obj_t mod_trezorcrypto_Sha512_make_new(const mp_obj_type_t *type,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha512_update(mp_obj_t self, mp_obj_t data) {
   mp_obj_Sha512_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   mp_get_buffer_raise(data, &msg, MP_BUFFER_READ);
   if (msg.len > 0) {
     sha512_Update(&(o->ctx), msg.buf, msg.len);
@@ -76,8 +76,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_Sha512_update_obj,
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_Sha512_digest(mp_obj_t self) {
   mp_obj_Sha512_t *o = MP_OBJ_TO_PTR(self);
-  uint8_t out[SHA512_DIGEST_LENGTH];
-  SHA512_CTX ctx;
+  uint8_t out[SHA512_DIGEST_LENGTH] = {0};
+  SHA512_CTX ctx = {0};
   memcpy(&ctx, &(o->ctx), sizeof(SHA512_CTX));
   sha512_Final(&ctx, out);
   memzero(&ctx, sizeof(SHA512_CTX));
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-shamir.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-shamir.h
index 5c75d0702..22336d20e 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-shamir.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-shamir.h
@@ -39,18 +39,18 @@
 ///     :rtype: Array of bytes.
 ///     """
 mp_obj_t mod_trezorcrypto_shamir_interpolate(mp_obj_t shares, mp_obj_t x) {
-  size_t share_count;
-  mp_obj_t *share_items;
+  size_t share_count = 0;
+  mp_obj_t *share_items = NULL;
   mp_obj_get_array(shares, &share_count, &share_items);
   if (share_count < 1 || share_count > SHAMIR_MAX_SHARE_COUNT) {
     mp_raise_ValueError("Invalid number of shares.");
   }
   uint8_t x_uint8 = trezor_obj_get_uint8(x);
-  uint8_t share_indices[SHAMIR_MAX_SHARE_COUNT];
-  const uint8_t *share_values[SHAMIR_MAX_SHARE_COUNT];
+  uint8_t share_indices[SHAMIR_MAX_SHARE_COUNT] = {0};
+  const uint8_t *share_values[SHAMIR_MAX_SHARE_COUNT] = {0};
   size_t value_len = 0;
   for (int i = 0; i < share_count; ++i) {
-    mp_obj_t *share;
+    mp_obj_t *share = NULL;
     mp_obj_get_array_fixed_n(share_items[i], 2, &share);
     share_indices[i] = trezor_obj_get_uint8(share[0]);
     mp_buffer_info_t value;
@@ -66,7 +66,7 @@ mp_obj_t mod_trezorcrypto_shamir_interpolate(mp_obj_t shares, mp_obj_t x) {
     }
     share_values[i] = value.buf;
   }
-  vstr_t vstr;
+  vstr_t vstr = {0};
   vstr_init_len(&vstr, value_len);
   if (shamir_interpolate((uint8_t *)vstr.buf, x_uint8, share_indices,
                          share_values, share_count, value_len) != true) {
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-slip39.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-slip39.h
index 43d2e664d..9adef554e 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-slip39.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-slip39.h
@@ -71,7 +71,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(
 ///     Raises ValueError if not found.
 ///     """
 STATIC mp_obj_t mod_trezorcrypto_slip39_word_index(mp_obj_t _word) {
-  mp_buffer_info_t word;
+  mp_buffer_info_t word = {0};
 
   mp_get_buffer_raise(_word, &word, MP_BUFFER_READ);
 
diff --git a/core/embed/extmod/modtrezorio/ff.c b/core/embed/extmod/modtrezorio/ff.c
index 2eefa982f..6e747433f 100644
--- a/core/embed/extmod/modtrezorio/ff.c
+++ b/core/embed/extmod/modtrezorio/ff.c
@@ -484,7 +484,7 @@ static const BYTE ExCvt[] = MKCVTBL(TBL_CT, FF_CODE_PAGE);
 
 static WORD ld_word (const BYTE* ptr)	/*	 Load a 2-byte little-endian word */
 {
-	WORD rv;
+	WORD rv = 0;
 
 	rv = ptr[1];
 	rv = rv << 8 | ptr[0];
@@ -493,7 +493,7 @@ static WORD ld_word (const BYTE* ptr)	/*	 Load a 2-byte little-endian word */
 
 static DWORD ld_dword (const BYTE* ptr)	/* Load a 4-byte little-endian word */
 {
-	DWORD rv;
+	DWORD rv = 0;
 
 	rv = ptr[3];
 	rv = rv << 8 | ptr[2];
@@ -563,11 +563,11 @@ static DWORD tchar2uni (	/* Returns a character in UTF-16 encoding (>=0x10000 on
 	const TCHAR** str		/* Pointer to pointer to TCHAR string in configured encoding */
 )
 {
-	DWORD uc;
+	DWORD uc = 0;
 	const TCHAR *p = *str;
 
-	BYTE b;
-	int nf;
+	BYTE b = 0;
+	int nf = 0;
 
 	uc = (BYTE)*p++;	/* Get an encoding unit */
 	if (uc & 0x80) {	/* Multiple byte code? */
@@ -605,7 +605,7 @@ static BYTE put_utf (	/* Returns number of encoding units written (0:buffer over
 	UINT szb	/* Size of the buffer */
 )
 {
-	DWORD hc;
+	DWORD hc = 0;
 
 	if (chr < 0x80) {	/* Single byte code? */
 		if (szb < 1) return 0;	/* Buffer overflow? */
@@ -702,7 +702,7 @@ static FRESULT sync_fs (	/* Returns FR_OK or FR_DISK_ERR */
 	FATFS* fs		/* Filesystem object */
 )
 {
-	FRESULT res;
+	FRESULT res = 0;
 
 
 	res = sync_window(fs);
@@ -756,8 +756,8 @@ static DWORD get_fat (		/* 0xFFFFFFFF:Disk error, 1:Internal error, 2..0x7FFFFFF
 	DWORD clst		/* Cluster number to get the value */
 )
 {
-	UINT wc, bc;
-	DWORD val;
+	UINT wc = 0, bc = 0;
+	DWORD val = 0;
 	FATFS *fs = obj->fs;
 
 
@@ -807,8 +807,8 @@ static FRESULT put_fat (	/* FR_OK(0):succeeded, !=0:error */
 	DWORD val		/* New value to be set to the entry */
 )
 {
-	UINT bc;
-	BYTE *p;
+	UINT bc = 0;
+	BYTE *p = NULL;
 	FRESULT res = FR_INT_ERR;
 
 
@@ -867,7 +867,7 @@ static FRESULT remove_chain (	/* FR_OK(0):succeeded, !=0:error */
 )
 {
 	FRESULT res = FR_OK;
-	DWORD nxt;
+	DWORD nxt = 0;
 	FATFS *fs = obj->fs;
 
 	if (clst < 2 || clst >= fs->n_fatent) return FR_INT_ERR;	/* Check if in valid range */
@@ -910,8 +910,8 @@ static DWORD create_chain (	/* 0:No free cluster, 1:Internal error, 0xFFFFFFFF:D
 	DWORD clst			/* Cluster# to stretch, 0:Create a new chain */
 )
 {
-	DWORD cs, ncl, scl;
-	FRESULT res;
+	DWORD cs = 0, ncl = 0, scl = 0;
+	FRESULT res = 0;
 	FATFS *fs = obj->fs;
 
 
@@ -989,9 +989,9 @@ static FRESULT dir_clear (	/* Returns FR_OK or FR_DISK_ERR */
 	DWORD clst		/* Directory table to clear */
 )
 {
-	LBA_t sect;
-	UINT n, szb;
-	BYTE *ibuf;
+	LBA_t sect = 0;
+	UINT n = 0, szb = 0;
+	BYTE *ibuf = NULL;
 
 
 	if (sync_window(fs) != FR_OK) return FR_DISK_ERR;	/* Flush disk access window */
@@ -1017,7 +1017,7 @@ static FRESULT dir_sdi (	/* FR_OK(0):succeeded, !=0:error */
 	DWORD ofs		/* Offset of directory table */
 )
 {
-	DWORD csz, clst;
+	DWORD csz = 0, clst = 0;
 	FATFS *fs = dp->obj.fs;
 
 
@@ -1065,7 +1065,7 @@ static FRESULT dir_next (	/* FR_OK(0):succeeded, FR_NO_FILE:End of table, FR_DEN
 	int stretch				/* 0: Do not stretch table, 1: Stretch table if needed */
 )
 {
-	DWORD ofs, clst;
+	DWORD ofs = 0, clst = 0;
 	FATFS *fs = dp->obj.fs;
 
 
@@ -1120,8 +1120,8 @@ static FRESULT dir_alloc (	/* FR_OK(0):succeeded, !=0:error */
 	UINT nent				/* Number of contiguous entries to allocate */
 )
 {
-	FRESULT res;
-	UINT n;
+	FRESULT res = 0;
+	UINT n = 0;
 	FATFS *fs = dp->obj.fs;
 
 
@@ -1157,7 +1157,7 @@ static DWORD ld_clust (	/* Returns the top cluster value of the SFN entry */
 	const BYTE* dir		/* Pointer to the key entry */
 )
 {
-	DWORD cl;
+	DWORD cl = 0;
 
 	cl = ld_word(dir + DIR_FstClusLO);
 	if (fs->fs_type == FS_FAT32) {
@@ -1191,8 +1191,8 @@ static int cmp_lfn (		/* 1:matched, 0:not matched */
 	BYTE* dir				/* Pointer to the directory entry containing the part of LFN */
 )
 {
-	UINT i, s;
-	WCHAR wc, uc;
+	UINT i = 0, s = 0;
+	WCHAR wc = 0, uc = 0;
 
 
 	if (ld_word(dir + LDIR_FstClusLO) != 0) return 0;	/* Check LDIR_FstClusLO */
@@ -1226,8 +1226,8 @@ static int pick_lfn (	/* 1:succeeded, 0:buffer overflow or invalid LFN entry */
 	BYTE* dir			/* Pointer to the LFN entry */
 )
 {
-	UINT i, s;
-	WCHAR wc, uc;
+	UINT i = 0, s = 0;
+	WCHAR wc = 0, uc = 0;
 
 
 	if (ld_word(dir + LDIR_FstClusLO) != 0) return 0;	/* Check LDIR_FstClusLO is 0 */
@@ -1264,8 +1264,8 @@ static void put_lfn (
 	BYTE sum			/* Checksum of the corresponding SFN */
 )
 {
-	UINT i, s;
-	WCHAR wc;
+	UINT i = 0, s = 0;
+	WCHAR wc = 0;
 
 
 	dir[LDIR_Chksum] = sum;			/* Set checksum */
@@ -1298,10 +1298,10 @@ static void gen_numname (
 	UINT seq			/* Sequence number */
 )
 {
-	BYTE ns[8], c;
-	UINT i, j;
-	WCHAR wc;
-	DWORD sreg;
+	BYTE ns[8] = {0}, c = 0;
+	UINT i = 0, j = 0;
+	WCHAR wc = 0;
+	DWORD sreg = 0;
 
 
 	mem_cpy(dst, src, 11);
@@ -1380,7 +1380,7 @@ static FRESULT dir_read (
 {
 	FRESULT res = FR_NO_FILE;
 	FATFS *fs = dp->obj.fs;
-	BYTE attr, b;
+	BYTE attr = 0, b = 0;
 	BYTE ord = 0xFF, sum = 0xFF;
 
 	while (dp->sect) {
@@ -1430,10 +1430,10 @@ static FRESULT dir_find (	/* FR_OK(0):succeeded, !=0:error */
 	DIR* dp					/* Pointer to the directory object with the file name */
 )
 {
-	FRESULT res;
+	FRESULT res = 0;
 	FATFS *fs = dp->obj.fs;
-	BYTE c;
-	BYTE a, ord, sum;
+	BYTE c = 0;
+	BYTE a = 0, ord = 0, sum = 0;
 
 	res = dir_sdi(dp, 0);			/* Rewind directory object */
 	if (res != FR_OK) return res;
@@ -1481,10 +1481,10 @@ static FRESULT dir_register (	/* FR_OK:succeeded, FR_DENIED:no free entry or too
 	DIR* dp						/* Target directory with object name to be created */
 )
 {
-	FRESULT res;
+	FRESULT res = 0;
 	FATFS *fs = dp->obj.fs;
-	UINT n, nlen, nent;
-	BYTE sn[12], sum;
+	UINT n = 0, nlen = 0, nent = 0;
+	BYTE sn[12] = {0}, sum = 0;
 
 
 	if (dp->fn[NSFLAG] & (NS_DOT | NS_NONAME)) return FR_INVALID_NAME;	/* Check name validity */
@@ -1547,7 +1547,7 @@ static FRESULT dir_remove (	/* FR_OK:Succeeded, FR_DISK_ERR:A disk error */
 	DIR* dp					/* Directory object pointing the entry to be removed */
 )
 {
-	FRESULT res;
+	FRESULT res = 0;
 	FATFS *fs = dp->obj.fs;
 	DWORD last = dp->dptr;
 
@@ -1583,9 +1583,9 @@ static void get_fileinfo (
 	FILINFO* fno		/* Pointer to the file information to be filled */
 )
 {
-	UINT si, di;
-	BYTE lcf;
-	WCHAR wc, hs;
+	UINT si = 0, di = 0;
+	BYTE lcf = 0;
+	WCHAR wc = 0, hs = 0;
 	FATFS *fs = dp->obj.fs;
 
 
@@ -1664,11 +1664,11 @@ static FRESULT create_name (	/* FR_OK: successful, FR_INVALID_NAME: could not cr
 	const TCHAR** path			/* Pointer to pointer to the segment in the path string */
 )
 {
-	BYTE b, cf;
-	WCHAR wc, *lfn;
-	DWORD uc;
-	UINT i, ni, si, di;
-	const TCHAR *p;
+	BYTE b = 0, cf = 0;
+	WCHAR wc = 0, *lfn = NULL;
+	DWORD uc = 0;
+	UINT i = 0, ni = 0, si = 0, di = 0;
+	const TCHAR *p = NULL;
 
 
 	/* Create LFN into LFN working buffer */
@@ -1780,8 +1780,8 @@ static FRESULT follow_path (	/* FR_OK(0): successful, !=0: error code */
 	const TCHAR* path			/* Full-path string to find a file or directory */
 )
 {
-	FRESULT res;
-	BYTE ns;
+	FRESULT res = 0;
+	BYTE ns = 0;
 	FATFS *fs = dp->obj.fs;
 
 
@@ -1837,9 +1837,9 @@ static int get_ldnumber (	/* Returns logical drive number (-1:invalid drive numb
 	const TCHAR** path		/* Pointer to pointer to the path name */
 )
 {
-	const TCHAR *tp, *tt;
-	TCHAR tc;
-	int i, vol = -1;
+	const TCHAR *tp = NULL, *tt = NULL;
+	TCHAR tc = 0;
+	int i = 0, vol = -1;
 
 	tt = tp = *path;
 	if (!tp) return vol;	/* Invalid path name? */
@@ -1905,8 +1905,8 @@ static UINT find_volume (	/* Returns BS status found in the hosting drive */
 	UINT part		/* Partition to fined = 0:auto, 1..:forced */
 )
 {
-	UINT fmt, i;
-	DWORD mbr_pt[4];
+	UINT fmt = 0, i = 0;
+	DWORD mbr_pt[4] = {0};
 
 
 	fmt = check_fs(fs, 0);				/* Load sector 0 and check if it is an FAT VBR as SFD */
@@ -1938,13 +1938,13 @@ static FRESULT mount_volume (	/* FR_OK(0): successful, !=0: an error occurred */
 	BYTE mode					/* !=0: Check write protection for write access */
 )
 {
-	int vol;
-	DSTATUS stat;
-	LBA_t bsect;
-	DWORD tsect, sysect, fasize, nclst, szbfat;
-	WORD nrsv;
-	FATFS *fs;
-	UINT fmt;
+	int vol = 0;
+	DSTATUS stat = 0;
+	LBA_t bsect = 0;
+	DWORD tsect = 0, sysect = 0, fasize = 0, nclst = 0, szbfat = 0;
+	WORD nrsv = 0;
+	FATFS *fs = NULL;
+	UINT fmt = 0;
 
 
 	/* Get logical drive number */
@@ -2120,9 +2120,9 @@ FRESULT f_mount (
 	BYTE opt			/* Mode option 0:Do not mount (delayed mount), 1:Mount immediately */
 )
 {
-	FATFS *cfs;
-	int vol;
-	FRESULT res;
+	FATFS *cfs = NULL;
+	int vol = 0;
+	FRESULT res = 0;
 	const TCHAR *rp = path;
 
 
@@ -2159,12 +2159,12 @@ FRESULT f_open (
 	BYTE mode			/* Access mode and file open mode flags */
 )
 {
-	FRESULT res;
-	DIR dj;
-	FATFS *fs;
-	DWORD cl, bcs, clst;
-	LBA_t sc;
-	FSIZE_t ofs;
+	FRESULT res = 0;
+	DIR dj = {0};
+	FATFS *fs = NULL;
+	DWORD cl = 0, bcs = 0, clst = 0;
+	LBA_t sc = 0;
+	FSIZE_t ofs = 0;
 	DEF_NAMBUF
 
 
@@ -2290,12 +2290,12 @@ FRESULT f_read (
 	UINT* br	/* Pointer to number of bytes read */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD clst;
-	LBA_t sect;
-	FSIZE_t remain;
-	UINT rcnt, cc, csect;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD clst = 0;
+	LBA_t sect = 0;
+	FSIZE_t remain = 0;
+	UINT rcnt = 0, cc = 0, csect = 0;
 	BYTE *rbuff = (BYTE*)buff;
 
 
@@ -2368,11 +2368,11 @@ FRESULT f_write (
 	UINT* bw			/* Pointer to number of bytes written */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD clst;
-	LBA_t sect;
-	UINT wcnt, cc, csect;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD clst = 0;
+	LBA_t sect = 0;
+	UINT wcnt = 0, cc = 0, csect = 0;
 	const BYTE *wbuff = (const BYTE*)buff;
 
 
@@ -2456,10 +2456,10 @@ FRESULT f_sync (
 	FIL* fp		/* Pointer to the file object */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD tm;
-	BYTE *dir;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD tm = 0;
+	BYTE *dir = NULL;
 
 
 	res = validate(&fp->obj, &fs);	/* Check validity of the file object */
@@ -2503,8 +2503,8 @@ FRESULT f_close (
 	FIL* fp		/* Pointer to the file object to be closed */
 )
 {
-	FRESULT res;
-	FATFS *fs;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
 
 	res = f_sync(fp);					/* Flush cached data */
 	if (res == FR_OK)
@@ -2532,11 +2532,11 @@ FRESULT f_lseek (
 	FSIZE_t ofs		/* File pointer from top of file */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD clst, bcs;
-	LBA_t nsect;
-	FSIZE_t ifptr;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD clst = 0, bcs = 0;
+	LBA_t nsect = 0;
+	FSIZE_t ifptr = 0;
 
 	res = validate(&fp->obj, &fs);		/* Check validity of the file object */
 	if (res == FR_OK) res = (FRESULT)fp->err;
@@ -2623,8 +2623,8 @@ FRESULT f_opendir (
 	const TCHAR* path	/* Pointer to the directory path */
 )
 {
-	FRESULT res;
-	FATFS *fs;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
 	DEF_NAMBUF
 
 
@@ -2670,8 +2670,8 @@ FRESULT f_closedir (
 	DIR *dp		/* Pointer to the directory object to be closed */
 )
 {
-	FRESULT res;
-	FATFS *fs;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
 
 
 	res = validate(&dp->obj, &fs);	/* Check validity of the file object */
@@ -2693,8 +2693,8 @@ FRESULT f_readdir (
 	FILINFO* fno		/* Pointer to file information to return */
 )
 {
-	FRESULT res;
-	FATFS *fs;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
 	DEF_NAMBUF
 
 
@@ -2731,8 +2731,8 @@ FRESULT f_stat (
 	FILINFO* fno		/* Pointer to file information to return */
 )
 {
-	FRESULT res;
-	DIR dj;
+	FRESULT res = 0;
+	DIR dj = {0};
 	DEF_NAMBUF
 
 
@@ -2766,12 +2766,12 @@ FRESULT f_getfree (
 	FATFS** fatfs		/* Pointer to return pointer to corresponding filesystem object */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD nfree, clst, stat;
-	LBA_t sect;
-	UINT i;
-	FFOBJID obj;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD nfree = 0, clst = 0, stat = 0;
+	LBA_t sect = 0;
+	UINT i = 0;
+	FFOBJID obj = {0};
 
 
 	/* Get logical drive */
@@ -2833,9 +2833,9 @@ FRESULT f_truncate (
 	FIL* fp		/* Pointer to the file object */
 )
 {
-	FRESULT res;
-	FATFS *fs;
-	DWORD ncl;
+	FRESULT res = 0;
+	FATFS *fs = NULL;
+	DWORD ncl = 0;
 
 
 	res = validate(&fp->obj, &fs);	/* Check validity of the file object */
@@ -2881,10 +2881,10 @@ FRESULT f_unlink (
 	const TCHAR* path		/* Pointer to the file or directory path */
 )
 {
-	FRESULT res;
-	DIR dj, sdj;
+	FRESULT res = 0;
+	DIR dj = {0}, sdj = {0};
 	DWORD dclst = 0;
-	FATFS *fs;
+	FATFS *fs = NULL;
 	DEF_NAMBUF
 
 
@@ -2947,11 +2947,11 @@ FRESULT f_mkdir (
 	const TCHAR* path		/* Pointer to the directory path */
 )
 {
-	FRESULT res;
-	DIR dj;
-	FFOBJID sobj;
-	FATFS *fs;
-	DWORD dcl, pcl, tm;
+	FRESULT res = 0;
+	DIR dj = {0};
+	FFOBJID sobj = {0};
+	FATFS *fs = NULL;
+	DWORD dcl = 0, pcl = 0, tm = 0;
 	DEF_NAMBUF
 
 
@@ -3021,11 +3021,11 @@ FRESULT f_rename (
 	const TCHAR* path_new	/* Pointer to the new name */
 )
 {
-	FRESULT res;
-	DIR djo, djn;
-	FATFS *fs;
-	BYTE buf[FF_FS_EXFAT ? SZDIRE * 2 : SZDIRE], *dir;
-	LBA_t sect;
+	FRESULT res = 0;
+	DIR djo = {0}, djn = {0};
+	FATFS *fs = NULL;
+	BYTE buf[(FF_FS_EXFAT) ? (SZDIRE * 2) : (SZDIRE)] = {0}, *dir = NULL;
+	LBA_t sect = 0;
 	DEF_NAMBUF
 
 
@@ -3099,11 +3099,11 @@ FRESULT f_getlabel (
 	DWORD* vsn			/* Variable to store the volume serial number */
 )
 {
-	FRESULT res;
-	DIR dj;
-	FATFS *fs;
-	UINT si, di;
-	WCHAR wc;
+	FRESULT res = 0;
+	DIR dj = {0};
+	FATFS *fs = NULL;
+	UINT si = 0, di = 0;
+	WCHAR wc = 0;
 
 	/* Get logical drive */
 	res = mount_volume(&path, &fs, 0);
@@ -3169,14 +3169,14 @@ FRESULT f_setlabel (
 	const TCHAR* label	/* Volume label to set with heading logical drive number */
 )
 {
-	FRESULT res;
-	DIR dj;
-	FATFS *fs;
-	BYTE dirvn[22];
-	UINT di;
-	WCHAR wc;
+	FRESULT res = 0;
+	DIR dj = {0};
+	FATFS *fs = NULL;
+	BYTE dirvn[22] = {0};
+	UINT di = 0;
+	WCHAR wc = 0;
 	static const char badchr[] = "+.,;=[]/\\\"*:<>\?|\x7F";	/* [0..] for FAT, [7..] for exFAT */
-	DWORD dc;
+	DWORD dc = 0;
 
 	/* Get logical drive */
 	res = mount_volume(&label, &fs, FA_WRITE);
@@ -3270,10 +3270,10 @@ static FRESULT create_partition (
 	BYTE* buf			/* Working buffer for a sector */
 )
 {
-	UINT i, cy;
-	LBA_t sz_drv;
-	DWORD sz_drv32, s_lba32, n_lba32;
-	BYTE *pte, hd, n_hd, sc, n_sc;
+	UINT i = 0, cy = 0;
+	LBA_t sz_drv = 0;
+	DWORD sz_drv32 = 0, s_lba32 = 0, n_lba32 = 0;
+	BYTE *pte = NULL, hd = 0, n_hd = 0, sc = 0, n_sc = 0;
 
 	/* Get drive size */
 	if (disk_ioctl(drv, GET_SECTOR_COUNT, &sz_drv) != RES_OK) return FR_DISK_ERR;
@@ -3332,16 +3332,16 @@ FRESULT f_mkfs (
 	static const WORD cst[] = {1, 4, 16, 64, 256, 512, 0};	/* Cluster size boundary for FAT volume (4Ks unit) */
 	static const WORD cst32[] = {1, 2, 4, 8, 16, 32, 0};	/* Cluster size boundary for FAT32 volume (128Ks unit) */
 	static const MKFS_PARM defopt = {FM_ANY, 0, 0, 0, 0};	/* Default parameter */
-	BYTE fsopt, fsty, sys, *buf, *pte, pdrv, ipart;
+	BYTE fsopt = 0, fsty = 0, sys = 0, *buf = NULL, *pte = NULL, pdrv = 0, ipart = 0;
 	WORD ss;	/* Sector size */
-	DWORD sz_buf, sz_blk, n_clst, pau, nsect, n;
+	DWORD sz_buf = 0, sz_blk = 0, n_clst = 0, pau = 0, nsect = 0, n = 0;
 	LBA_t sz_vol, b_vol, b_fat, b_data;		/* Size of volume, Base LBA of volume, fat, data */
-	LBA_t sect, lba[2];
+	LBA_t sect = 0, lba[2] = {0};
 	DWORD sz_rsv, sz_fat, sz_dir, sz_au;	/* Size of reserved, fat, dir, data, cluster */
 	UINT n_fat, n_root, i;					/* Index, Number of FATs and Number of roor dir entries */
-	int vol;
-	DSTATUS ds;
-	FRESULT fr;
+	int vol = 0;
+	DSTATUS ds = 0;
+	FRESULT fr = 0;
 
 
 	/* Check mounted drive and clear work area */
diff --git a/core/embed/extmod/modtrezorio/ffunicode.c b/core/embed/extmod/modtrezorio/ffunicode.c
index 42f3b57b1..3267a822f 100644
--- a/core/embed/extmod/modtrezorio/ffunicode.c
+++ b/core/embed/extmod/modtrezorio/ffunicode.c
@@ -129,8 +129,8 @@ DWORD ff_wtoupper (	/* Returns up-converted code point */
 	DWORD uni		/* Unicode code point to be up-converted */
 )
 {
-	const WORD *p;
-	WORD uc, bc, nc, cmd;
+	const WORD *p = (void*) 0;
+	WORD uc = 0, bc = 0, nc = 0, cmd = 0;
 	static const WORD cvt1[] = {	/* Compressed up conversion table for U+0000 - U+0FFF */
 		/* Basic Latin */
 		0x0061,0x031A,
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-fatfs.h b/core/embed/extmod/modtrezorio/modtrezorio-fatfs.h
index eb620ca66..a7ce142cf 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-fatfs.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-fatfs.h
@@ -211,9 +211,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_FatFSFile_close_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_FatFSFile_read(mp_obj_t self, mp_obj_t data) {
   mp_obj_FatFSFile_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(data, &buf, MP_BUFFER_WRITE);
-  UINT read;
+  UINT read = 0;
   FRESULT res = f_read(&(o->fp), buf.buf, buf.len, &read);
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -229,9 +229,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorio_FatFSFile_read_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_FatFSFile_write(mp_obj_t self, mp_obj_t data) {
   mp_obj_FatFSFile_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(data, &buf, MP_BUFFER_READ);
-  UINT written;
+  UINT written = 0;
   FRESULT res = f_write(&(o->fp), buf.buf, buf.len, &written);
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -327,7 +327,7 @@ typedef struct _mp_obj_FatFSDir_t {
 ///     """
 STATIC mp_obj_t mod_trezorio_FatFSDir_iternext(mp_obj_t self) {
   mp_obj_FatFSDir_t *o = MP_OBJ_TO_PTR(self);
-  FILINFO info;
+  FILINFO info = {0};
   FRESULT res = f_readdir(&(o->dp), &info);
   if (res != FR_OK) {
     f_closedir(&(o->dp));
@@ -357,7 +357,7 @@ STATIC const mp_obj_type_t mod_trezorio_FatFSDir_type = {
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_open(mp_obj_t path, mp_obj_t flags) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _path, _flags;
+  mp_buffer_info_t _path = {0}, _flags = {0};
   mp_get_buffer_raise(path, &_path, MP_BUFFER_READ);
   mp_get_buffer_raise(flags, &_flags, MP_BUFFER_READ);
   const char *mode_s = _flags.buf;
@@ -381,7 +381,7 @@ STATIC mp_obj_t mod_trezorio_fatfs_open(mp_obj_t path, mp_obj_t flags) {
         break;
     }
   }
-  FIL fp;
+  FIL fp = {0};
   FRESULT res = f_open(&fp, _path.buf, mode);
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -400,9 +400,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorio_fatfs_open_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_listdir(mp_obj_t path) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _path;
+  mp_buffer_info_t _path = {0};
   mp_get_buffer_raise(path, &_path, MP_BUFFER_READ);
-  DIR dp;
+  DIR dp = {0};
   FRESULT res = f_opendir(&dp, _path.buf);
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -421,7 +421,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_fatfs_listdir_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_mkdir(size_t n_args, const mp_obj_t *args) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t path;
+  mp_buffer_info_t path = {0};
   mp_get_buffer_raise(args[0], &path, MP_BUFFER_READ);
   FRESULT res = f_mkdir(path.buf);
   // directory exists and exist_ok is True, return without failure
@@ -442,7 +442,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorio_fatfs_mkdir_obj, 1, 2,
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_unlink(mp_obj_t path) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _path;
+  mp_buffer_info_t _path = {0};
   mp_get_buffer_raise(path, &_path, MP_BUFFER_READ);
   FRESULT res = f_unlink(_path.buf);
   if (res != FR_OK) {
@@ -459,9 +459,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_fatfs_unlink_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_stat(mp_obj_t path) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _path;
+  mp_buffer_info_t _path = {0};
   mp_get_buffer_raise(path, &_path, MP_BUFFER_READ);
-  FILINFO info;
+  FILINFO info = {0};
   FRESULT res = f_stat(_path.buf, &info);
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -477,7 +477,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_fatfs_stat_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_fatfs_rename(mp_obj_t oldpath, mp_obj_t newpath) {
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _oldpath, _newpath;
+  mp_buffer_info_t _oldpath = {0}, _newpath = {0};
   mp_get_buffer_raise(oldpath, &_oldpath, MP_BUFFER_READ);
   mp_get_buffer_raise(newpath, &_newpath, MP_BUFFER_READ);
   FRESULT res = f_rename(_oldpath.buf, _newpath.buf);
@@ -537,7 +537,7 @@ STATIC mp_obj_t mod_trezorio_fatfs_mkfs() {
     FATFS_RAISE(FatFSError, FR_LOCKED);
   }
   MKFS_PARM params = {FM_FAT32, 0, 0, 0, 0};
-  uint8_t working_buf[FF_MAX_SS];
+  uint8_t working_buf[FF_MAX_SS] = {0};
   FRESULT res = f_mkfs("", &params, working_buf, sizeof(working_buf));
   if (res != FR_OK) {
     FATFS_RAISE(FatFSError, res);
@@ -556,7 +556,7 @@ STATIC mp_obj_t mod_trezorio_fatfs_setlabel(mp_obj_t label) {
   having parsed the FAT table, which is of course a prerequisite for setting
   label. */
   FATFS_ONLY_MOUNTED;
-  mp_buffer_info_t _label;
+  mp_buffer_info_t _label = {0};
   mp_get_buffer_raise(label, &_label, MP_BUFFER_READ);
   FRESULT res = f_setlabel(_label.buf);
   if (res != FR_OK) {
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-flash.h b/core/embed/extmod/modtrezorio/modtrezorio-flash.h
index 3f906b906..11c00250d 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-flash.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-flash.h
@@ -50,7 +50,7 @@ STATIC mp_obj_t mod_trezorio_FlashOTP_write(size_t n_args,
                                             const mp_obj_t *args) {
   uint8_t block = trezor_obj_get_uint8(args[1]);
   uint8_t offset = trezor_obj_get_uint8(args[2]);
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[3], &data, MP_BUFFER_READ);
   if (sectrue != flash_otp_write(block, offset, data.buf, data.len)) {
     mp_raise_ValueError("write failed");
@@ -68,7 +68,7 @@ STATIC mp_obj_t mod_trezorio_FlashOTP_read(size_t n_args,
                                            const mp_obj_t *args) {
   uint8_t block = trezor_obj_get_uint8(args[1]);
   uint8_t offset = trezor_obj_get_uint8(args[2]);
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[3], &data, MP_BUFFER_WRITE);
   if (sectrue != flash_otp_read(block, offset, data.buf, data.len)) {
     mp_raise_ValueError("read failed");
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-hid.h b/core/embed/extmod/modtrezorio/modtrezorio-hid.h
index 9acabb093..532dc8ce5 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-hid.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-hid.h
@@ -62,7 +62,7 @@ STATIC mp_obj_t mod_trezorio_HID_make_new(const mp_obj_type_t *type,
        MP_ARG_REQUIRED | MP_ARG_KW_ONLY | MP_ARG_OBJ,
        {.u_obj = MP_OBJ_NULL}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
@@ -73,7 +73,7 @@ STATIC mp_obj_t mod_trezorio_HID_make_new(const mp_obj_type_t *type,
   const mp_int_t protocol = vals[4].u_int;
   const mp_int_t polling_interval = vals[5].u_int;
   const mp_int_t max_packet_len = vals[6].u_int;
-  mp_buffer_info_t report_desc;
+  mp_buffer_info_t report_desc = {0};
   mp_get_buffer_raise(vals[7].u_obj, &report_desc, MP_BUFFER_READ);
 
   if (report_desc.buf == NULL || report_desc.len == 0 ||
@@ -122,7 +122,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_HID_iface_num_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_HID_write(mp_obj_t self, mp_obj_t msg) {
   mp_obj_HID_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(msg, &buf, MP_BUFFER_READ);
   ssize_t r = usb_hid_write(o->info.iface_num, buf.buf, buf.len);
   return MP_OBJ_NEW_SMALL_INT(r);
@@ -137,7 +137,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorio_HID_write_obj,
 STATIC mp_obj_t mod_trezorio_HID_write_blocking(mp_obj_t self, mp_obj_t msg,
                                                 mp_obj_t timeout_ms) {
   mp_obj_HID_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(msg, &buf, MP_BUFFER_READ);
   uint32_t timeout = trezor_obj_get_uint(timeout_ms);
   ssize_t r =
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-poll.h b/core/embed/extmod/modtrezorio/modtrezorio-poll.h
index 307e74039..f771bd9bc 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-poll.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-poll.h
@@ -50,11 +50,11 @@ STATIC mp_obj_t mod_trezorio_poll(mp_obj_t ifaces, mp_obj_t list_ref,
 
   const mp_uint_t timeout = trezor_obj_get_uint(timeout_ms);
   const mp_uint_t deadline = mp_hal_ticks_ms() + timeout;
-  mp_obj_iter_buf_t iterbuf;
+  mp_obj_iter_buf_t iterbuf = {0};
 
   for (;;) {
     mp_obj_t iter = mp_getiter(ifaces, &iterbuf);
-    mp_obj_t item;
+    mp_obj_t item = 0;
     while ((item = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
       const mp_uint_t i = trezor_obj_get_uint(item);
       const mp_uint_t iface = i & 0x00FF;
@@ -96,7 +96,7 @@ STATIC mp_obj_t mod_trezorio_poll(mp_obj_t ifaces, mp_obj_t list_ref,
         }
       } else if (mode == POLL_READ) {
         if (sectrue == usb_hid_can_read(iface)) {
-          uint8_t buf[64];
+          uint8_t buf[64] = {0};
           int len = usb_hid_read(iface, buf, sizeof(buf));
           if (len > 0) {
             ret->items[0] = MP_OBJ_NEW_SMALL_INT(i);
@@ -104,7 +104,7 @@ STATIC mp_obj_t mod_trezorio_poll(mp_obj_t ifaces, mp_obj_t list_ref,
             return mp_const_true;
           }
         } else if (sectrue == usb_webusb_can_read(iface)) {
-          uint8_t buf[64];
+          uint8_t buf[64] = {0};
           int len = usb_webusb_read(iface, buf, sizeof(buf));
           if (len > 0) {
             ret->items[0] = MP_OBJ_NEW_SMALL_INT(i);
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-sdcard.h b/core/embed/extmod/modtrezorio/modtrezorio-sdcard.h
index 9dd92be22..1750f5854 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-sdcard.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-sdcard.h
@@ -82,7 +82,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorio_sdcard_capacity_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_sdcard_read(mp_obj_t block_num, mp_obj_t buf) {
   uint32_t block = trezor_obj_get_uint(block_num);
-  mp_buffer_info_t bufinfo;
+  mp_buffer_info_t bufinfo = {0};
   mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_WRITE);
   if (sectrue !=
       sdcard_read_blocks(bufinfo.buf, block, bufinfo.len / SDCARD_BLOCK_SIZE)) {
@@ -101,7 +101,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorio_sdcard_read_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_sdcard_write(mp_obj_t block_num, mp_obj_t buf) {
   uint32_t block = trezor_obj_get_uint(block_num);
-  mp_buffer_info_t bufinfo;
+  mp_buffer_info_t bufinfo = {0};
   mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_READ);
   if (sectrue != sdcard_write_blocks(bufinfo.buf, block,
                                      bufinfo.len / SDCARD_BLOCK_SIZE)) {
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-usb.h b/core/embed/extmod/modtrezorio/modtrezorio-usb.h
index b75afb471..98bc40a96 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-usb.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-usb.h
@@ -99,7 +99,7 @@ STATIC mp_obj_t mod_trezorio_USB_make_new(const mp_obj_type_t *type,
       {MP_QSTR_usb21_enabled, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true}},
       {MP_QSTR_usb21_landing, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
@@ -186,8 +186,8 @@ STATIC mp_obj_t mod_trezorio_USB_open(mp_obj_t self) {
     mp_raise_msg(&mp_type_RuntimeError, "already initialized");
   }
 
-  size_t iface_cnt;
-  mp_obj_t *iface_objs;
+  size_t iface_cnt = 0;
+  mp_obj_t *iface_objs = NULL;
   mp_obj_get_array(MP_OBJ_FROM_PTR(&o->ifaces), &iface_cnt, &iface_objs);
 
   // Initialize the USB stack
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-vcp.h b/core/embed/extmod/modtrezorio/modtrezorio-vcp.h
index 2253e2857..6a427c041 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-vcp.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-vcp.h
@@ -60,7 +60,7 @@ STATIC mp_obj_t mod_trezorio_VCP_make_new(const mp_obj_type_t *type,
        MP_ARG_REQUIRED | MP_ARG_KW_ONLY | MP_ARG_INT,
        {.u_int = 0}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
diff --git a/core/embed/extmod/modtrezorio/modtrezorio-webusb.h b/core/embed/extmod/modtrezorio/modtrezorio-webusb.h
index 55f07cc39..e18ba38cf 100644
--- a/core/embed/extmod/modtrezorio/modtrezorio-webusb.h
+++ b/core/embed/extmod/modtrezorio/modtrezorio-webusb.h
@@ -58,7 +58,7 @@ STATIC mp_obj_t mod_trezorio_WebUSB_make_new(const mp_obj_type_t *type,
       {MP_QSTR_polling_interval, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1}},
       {MP_QSTR_max_packet_len, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 64}},
   };
-  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
+  mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)] = {0};
   mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args),
                             allowed_args, vals);
 
@@ -110,7 +110,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorio_WebUSB_iface_num_obj,
 ///     """
 STATIC mp_obj_t mod_trezorio_WebUSB_write(mp_obj_t self, mp_obj_t msg) {
   mp_obj_WebUSB_t *o = MP_OBJ_TO_PTR(self);
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(msg, &buf, MP_BUFFER_READ);
   ssize_t r = usb_webusb_write(o->info.iface_num, buf.buf, buf.len);
   return MP_OBJ_NEW_SMALL_INT(r);
diff --git a/core/embed/extmod/modtrezorui/display-stm32_T.h b/core/embed/extmod/modtrezorui/display-stm32_T.h
index 086ad7a34..f8568ff9e 100644
--- a/core/embed/extmod/modtrezorui/display-stm32_T.h
+++ b/core/embed/extmod/modtrezorui/display-stm32_T.h
@@ -44,7 +44,7 @@
   0x009341U  // section "8.3.23 Read ID4 (D3h)" of ILI9341V datasheet
 
 static uint32_t read_display_id(uint8_t command) {
-  volatile uint8_t c;
+  volatile uint8_t c = 0;
   uint32_t id = 0;
   CMD(command);
   c = ADDR;  // first returned value is a dummy value and should be discarded
diff --git a/core/embed/extmod/modtrezorui/display-unix.h b/core/embed/extmod/modtrezorui/display-unix.h
index d5fcf2b6a..3c87f32ca 100644
--- a/core/embed/extmod/modtrezorui/display-unix.h
+++ b/core/embed/extmod/modtrezorui/display-unix.h
@@ -101,7 +101,7 @@ void display_init(void) {
   }
   atexit(SDL_Quit);
 
-  char *window_title;
+  char *window_title = NULL;
   if (!asprintf(&window_title, "Trezor^emu: %s", profile_name())) {
     window_title = "Trezor^emu";
   }
diff --git a/core/embed/extmod/modtrezorui/display.c b/core/embed/extmod/modtrezorui/display.c
index eb7f70b84..d1b5ca1cc 100644
--- a/core/embed/extmod/modtrezorui/display.c
+++ b/core/embed/extmod/modtrezorui/display.c
@@ -88,7 +88,7 @@ static struct { int x, y; } DISPLAY_OFFSET;
 
 static inline uint16_t interpolate_color(uint16_t color0, uint16_t color1,
                                          uint8_t step) {
-  uint8_t cr, cg, cb;
+  uint8_t cr = 0, cg = 0, cb = 0;
   cr = (((color0 & 0xF800) >> 11) * step +
         ((color1 & 0xF800) >> 11) * (15 - step)) /
        15;
@@ -133,7 +133,7 @@ void display_clear(void) {
 void display_bar(int x, int y, int w, int h, uint16_t c) {
   x += DISPLAY_OFFSET.x;
   y += DISPLAY_OFFSET.y;
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, w, h, &x0, &y0, &x1, &y1);
   display_set_window(x0, y0, x1, y1);
   for (int i = 0; i < (x1 - x0 + 1) * (y1 - y0 + 1); i++) {
@@ -167,11 +167,11 @@ void display_bar_radius(int x, int y, int w, int h, uint16_t c, uint16_t b,
   } else {
     r = 16 / r;
   }
-  uint16_t colortable[16];
+  uint16_t colortable[16] = {0};
   set_color_table(colortable, c, b);
   x += DISPLAY_OFFSET.x;
   y += DISPLAY_OFFSET.y;
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, w, h, &x0, &y0, &x1, &y1);
   display_set_window(x0, y0, x1, y1);
   for (int j = y0; j <= y1; j++) {
@@ -220,7 +220,7 @@ void display_image(int x, int y, int w, int h, const void *data,
 #if TREZOR_MODEL == T
   x += DISPLAY_OFFSET.x;
   y += DISPLAY_OFFSET.y;
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, w, h, &x0, &y0, &x1, &y1);
   display_set_window(x0, y0, x1, y1);
   x0 -= x;
@@ -228,9 +228,9 @@ void display_image(int x, int y, int w, int h, const void *data,
   y0 -= y;
   y1 -= y;
 
-  struct uzlib_uncomp decomp;
-  uint8_t decomp_window[UZLIB_WINDOW_SIZE];
-  uint8_t decomp_out[2];
+  struct uzlib_uncomp decomp = {0};
+  uint8_t decomp_window[UZLIB_WINDOW_SIZE] = {0};
+  uint8_t decomp_out[2] = {0};
   uzlib_prepare(&decomp, decomp_window, data, datalen, decomp_out,
                 sizeof(decomp_out));
 
@@ -260,7 +260,7 @@ void display_avatar(int x, int y, const void *data, uint32_t datalen,
 #if TREZOR_MODEL == T
   x += DISPLAY_OFFSET.x;
   y += DISPLAY_OFFSET.y;
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, AVATAR_IMAGE_SIZE, AVATAR_IMAGE_SIZE, &x0, &y0, &x1, &y1);
   display_set_window(x0, y0, x1, y1);
   x0 -= x;
@@ -268,9 +268,9 @@ void display_avatar(int x, int y, const void *data, uint32_t datalen,
   y0 -= y;
   y1 -= y;
 
-  struct uzlib_uncomp decomp;
-  uint8_t decomp_window[UZLIB_WINDOW_SIZE];
-  uint8_t decomp_out[2];
+  struct uzlib_uncomp decomp = {0};
+  uint8_t decomp_window[UZLIB_WINDOW_SIZE] = {0};
+  uint8_t decomp_out[2] = {0};
   uzlib_prepare(&decomp, decomp_window, data, datalen, decomp_out,
                 sizeof(decomp_out));
 
@@ -295,7 +295,7 @@ void display_avatar(int x, int y, const void *data, uint32_t datalen,
 #if AVATAR_ANTIALIAS
         d = 31 * (d - AVATAR_BORDER_LOW) /
             (AVATAR_BORDER_HIGH - AVATAR_BORDER_LOW);
-        uint16_t c;
+        uint16_t c = 0;
         if (d >= 16) {
           c = interpolate_color(bgcolor, fgcolor, d - 16);
         } else {
@@ -318,7 +318,7 @@ void display_icon(int x, int y, int w, int h, const void *data,
   x += DISPLAY_OFFSET.x;
   y += DISPLAY_OFFSET.y;
   x &= ~1;  // cannot draw at odd coordinate
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, w, h, &x0, &y0, &x1, &y1);
   display_set_window(x0, y0, x1, y1);
   x0 -= x;
@@ -326,12 +326,12 @@ void display_icon(int x, int y, int w, int h, const void *data,
   y0 -= y;
   y1 -= y;
 
-  uint16_t colortable[16];
+  uint16_t colortable[16] = {0};
   set_color_table(colortable, fgcolor, bgcolor);
 
-  struct uzlib_uncomp decomp;
-  uint8_t decomp_window[UZLIB_WINDOW_SIZE];
-  uint8_t decomp_out;
+  struct uzlib_uncomp decomp = {0};
+  uint8_t decomp_window[UZLIB_WINDOW_SIZE] = {0};
+  uint8_t decomp_out = 0;
   uzlib_prepare(&decomp, decomp_window, data, datalen, &decomp_out,
                 sizeof(decomp_out));
 
@@ -357,7 +357,7 @@ void display_loader(uint16_t progress, bool indeterminate, int yoffset,
                     uint16_t fgcolor, uint16_t bgcolor, const uint8_t *icon,
                     uint32_t iconlen, uint16_t iconfgcolor) {
 #if TREZOR_MODEL == T
-  uint16_t colortable[16], iconcolortable[16];
+  uint16_t colortable[16] = {0}, iconcolortable[16] = {0};
   set_color_table(colortable, fgcolor, bgcolor);
   if (icon) {
     set_color_table(iconcolortable, iconfgcolor, bgcolor);
@@ -374,9 +374,9 @@ void display_loader(uint16_t progress, bool indeterminate, int yoffset,
       LOADER_ICON_SIZE == *(uint16_t *)(icon + 4) &&
       LOADER_ICON_SIZE == *(uint16_t *)(icon + 6) &&
       iconlen == 12 + *(uint32_t *)(icon + 8)) {
-    uint8_t icondata[LOADER_ICON_SIZE * LOADER_ICON_SIZE / 2];
+    uint8_t icondata[(LOADER_ICON_SIZE * LOADER_ICON_SIZE) / 2] = {0};
     memzero(&icondata, sizeof(icondata));
-    struct uzlib_uncomp decomp;
+    struct uzlib_uncomp decomp = {0};
     uzlib_prepare(&decomp, NULL, icon + 12, iconlen - 12, icondata,
                   sizeof(icondata));
     uzlib_uncompress(&decomp);
@@ -387,7 +387,7 @@ void display_loader(uint16_t progress, bool indeterminate, int yoffset,
   for (int y = 0; y < img_loader_size * 2; y++) {
     for (int x = 0; x < img_loader_size * 2; x++) {
       int mx = x, my = y;
-      uint16_t a;
+      uint16_t a = 0;
       if ((mx >= img_loader_size) && (my >= img_loader_size)) {
         mx = img_loader_size * 2 - 1 - x;
         my = img_loader_size * 2 - 1 - y;
@@ -411,7 +411,7 @@ void display_loader(uint16_t progress, bool indeterminate, int yoffset,
         int i =
             (x - (img_loader_size - (LOADER_ICON_SIZE / 2))) +
             (y - (img_loader_size - (LOADER_ICON_SIZE / 2))) * LOADER_ICON_SIZE;
-        uint8_t c;
+        uint8_t c = 0;
         if (i % 2) {
           c = icon[i / 2] & 0x0F;
         } else {
@@ -419,7 +419,7 @@ void display_loader(uint16_t progress, bool indeterminate, int yoffset,
         }
         PIXELDATA(iconcolortable[c]);
       } else {
-        uint8_t c;
+        uint8_t c = 0;
         if (indeterminate) {
           uint16_t diff =
               (progress > a) ? (progress - a) : (1000 + progress - a);
@@ -505,7 +505,7 @@ void display_print(const char *text, int textlen) {
     y /= 8;
     const int k = x % 6;
     x /= 6;
-    char c;
+    char c = 0;
     if (x < DISPLAY_PRINT_COLS && y < DISPLAY_PRINT_ROWS) {
       c = display_print_buf[y][x] & 0x7F;
       // char invert = display_print_buf[y][x] & 0x80;
@@ -539,7 +539,7 @@ void display_printf(const char *fmt, ...) {
   } else {
     va_list va;
     va_start(va, fmt);
-    char buf[256];
+    char buf[256] = {0};
     int len = mini_vsnprintf(buf, sizeof(buf), fmt, va);
     display_print(buf, len);
     va_end(va);
@@ -633,7 +633,7 @@ static void display_text_render(int x, int y, const char *text, int textlen,
     textlen = strlen(text);
   }
 
-  uint16_t colortable[16];
+  uint16_t colortable[16] = {0};
   set_color_table(colortable, fgcolor, bgcolor);
 
   // render glyphs
@@ -648,7 +648,7 @@ static void display_text_render(int x, int y, const char *text, int textlen,
     if (w && h) {
       const int sx = x + bearX;
       const int sy = y - bearY;
-      int x0, y0, x1, y1;
+      int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
       clamp_coords(sx, sy, w, h, &x0, &y0, &x1, &y1);
       display_set_window(x0, y0, x1, y1);
       for (int j = y0; j <= y1; j++) {
@@ -759,8 +759,8 @@ void display_qrcode(int x, int y, const char *data, uint32_t datalen,
                     uint8_t scale) {
   if (scale < 1 || scale > 10) return;
 
-  uint8_t codedata[qrcodegen_BUFFER_LEN_FOR_VERSION(QR_MAX_VERSION)];
-  uint8_t tempdata[qrcodegen_BUFFER_LEN_FOR_VERSION(QR_MAX_VERSION)];
+  uint8_t codedata[qrcodegen_BUFFER_LEN_FOR_VERSION(QR_MAX_VERSION)] = {0};
+  uint8_t tempdata[qrcodegen_BUFFER_LEN_FOR_VERSION(QR_MAX_VERSION)] = {0};
 
   int side = 0;
   if (qrcodegen_encodeText(data, tempdata, codedata, qrcodegen_Ecc_MEDIUM,
@@ -771,7 +771,7 @@ void display_qrcode(int x, int y, const char *data, uint32_t datalen,
 
   x += DISPLAY_OFFSET.x - (side + 2) * scale / 2;
   y += DISPLAY_OFFSET.y - (side + 2) * scale / 2;
-  int x0, y0, x1, y1;
+  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
   clamp_coords(x, y, (side + 2) * scale, (side + 2) * scale, &x0, &y0, &x1,
                &y1);
   display_set_window(x0, y0, x1, y1);
diff --git a/core/embed/extmod/modtrezorui/modtrezorui-display.h b/core/embed/extmod/modtrezorui/modtrezorui-display.h
index da049891c..72de5f6f4 100644
--- a/core/embed/extmod/modtrezorui/modtrezorui-display.h
+++ b/core/embed/extmod/modtrezorui/modtrezorui-display.h
@@ -128,7 +128,7 @@ STATIC mp_obj_t mod_trezorui_Display_image(size_t n_args,
                                            const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t image;
+  mp_buffer_info_t image = {0};
   mp_get_buffer_raise(args[3], &image, MP_BUFFER_READ);
   const uint8_t *data = image.buf;
   if (image.len < 8 || memcmp(data, "TOIf", 4) != 0) {
@@ -159,7 +159,7 @@ STATIC mp_obj_t mod_trezorui_Display_avatar(size_t n_args,
                                             const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t image;
+  mp_buffer_info_t image = {0};
   mp_get_buffer_raise(args[3], &image, MP_BUFFER_READ);
   const uint8_t *data = image.buf;
   if (image.len < 8 || memcmp(data, "TOIf", 4) != 0) {
@@ -193,7 +193,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_avatar_obj, 6,
 STATIC mp_obj_t mod_trezorui_Display_icon(size_t n_args, const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t icon;
+  mp_buffer_info_t icon = {0};
   mp_get_buffer_raise(args[3], &icon, MP_BUFFER_READ);
   const uint8_t *data = icon.buf;
   if (icon.len < 8 || memcmp(data, "TOIg", 4) != 0) {
@@ -239,7 +239,7 @@ STATIC mp_obj_t mod_trezorui_Display_loader(size_t n_args,
   mp_int_t fgcolor = mp_obj_get_int(args[4]);
   mp_int_t bgcolor = mp_obj_get_int(args[5]);
   if (n_args > 6) {  // icon provided
-    mp_buffer_info_t icon;
+    mp_buffer_info_t icon = {0};
     mp_get_buffer_raise(args[6], &icon, MP_BUFFER_READ);
     const uint8_t *data = icon.buf;
     if (icon.len < 8 || memcmp(data, "TOIg", 4) != 0) {
@@ -254,7 +254,7 @@ STATIC mp_obj_t mod_trezorui_Display_loader(size_t n_args,
     if (datalen != icon.len - 12) {
       mp_raise_ValueError("Invalid size of data");
     }
-    uint16_t iconfgcolor;
+    uint16_t iconfgcolor = 0;
     if (n_args > 7) {  // icon color provided
       iconfgcolor = mp_obj_get_int(args[7]);
     } else {
@@ -276,7 +276,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_loader_obj, 6,
 ///     Renders text using 5x8 bitmap font (using special text mode).
 ///     """
 STATIC mp_obj_t mod_trezorui_Display_print(mp_obj_t self, mp_obj_t text) {
-  mp_buffer_info_t buf;
+  mp_buffer_info_t buf = {0};
   mp_get_buffer_raise(text, &buf, MP_BUFFER_READ);
   if (buf.len > 0) {
     display_print(buf.buf, buf.len);
@@ -305,7 +305,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorui_Display_print_obj,
 STATIC mp_obj_t mod_trezorui_Display_text(size_t n_args, const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t text;
+  mp_buffer_info_t text = {0};
   mp_get_buffer_raise(args[3], &text, MP_BUFFER_READ);
   mp_int_t font = mp_obj_get_int(args[4]);
   mp_int_t fgcolor = mp_obj_get_int(args[5]);
@@ -342,7 +342,7 @@ STATIC mp_obj_t mod_trezorui_Display_text_center(size_t n_args,
                                                  const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t text;
+  mp_buffer_info_t text = {0};
   mp_get_buffer_raise(args[3], &text, MP_BUFFER_READ);
   mp_int_t font = mp_obj_get_int(args[4]);
   mp_int_t fgcolor = mp_obj_get_int(args[5]);
@@ -380,7 +380,7 @@ STATIC mp_obj_t mod_trezorui_Display_text_right(size_t n_args,
                                                 const mp_obj_t *args) {
   mp_int_t x = mp_obj_get_int(args[1]);
   mp_int_t y = mp_obj_get_int(args[2]);
-  mp_buffer_info_t text;
+  mp_buffer_info_t text = {0};
   mp_get_buffer_raise(args[3], &text, MP_BUFFER_READ);
   mp_int_t font = mp_obj_get_int(args[4]);
   mp_int_t fgcolor = mp_obj_get_int(args[5]);
@@ -404,7 +404,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_text_right_obj,
 ///     """
 STATIC mp_obj_t mod_trezorui_Display_text_width(mp_obj_t self, mp_obj_t text,
                                                 mp_obj_t font) {
-  mp_buffer_info_t txt;
+  mp_buffer_info_t txt = {0};
   mp_get_buffer_raise(text, &txt, MP_BUFFER_READ);
   mp_int_t f = mp_obj_get_int(font);
   int w = display_text_width(txt.buf, txt.len, f);
@@ -421,7 +421,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorui_Display_text_width_obj,
 ///     """
 STATIC mp_obj_t mod_trezorui_Display_text_split(size_t n_args,
                                                 const mp_obj_t *args) {
-  mp_buffer_info_t text;
+  mp_buffer_info_t text = {0};
   mp_get_buffer_raise(args[1], &text, MP_BUFFER_READ);
   mp_int_t font = mp_obj_get_int(args[2]);
   mp_int_t requested_width = mp_obj_get_int(args[3]);
@@ -445,7 +445,7 @@ STATIC mp_obj_t mod_trezorui_Display_qrcode(size_t n_args,
   if (scale < 1 || scale > 10) {
     mp_raise_ValueError("Scale has to be between 1 and 10");
   }
-  mp_buffer_info_t data;
+  mp_buffer_info_t data = {0};
   mp_get_buffer_raise(args[3], &data, MP_BUFFER_READ);
   if (data.len > 0) {
     display_qrcode(x, y, data.buf, data.len, scale);
@@ -510,10 +510,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_backlight_obj,
 ///     """
 STATIC mp_obj_t mod_trezorui_Display_offset(size_t n_args,
                                             const mp_obj_t *args) {
-  int xy[2], x, y;
+  int xy[2] = {0}, x = 0, y = 0;
   if (n_args > 1) {
-    size_t xy_cnt;
-    mp_obj_t *xy_obj;
+    size_t xy_cnt = 0;
+    mp_obj_t *xy_obj = NULL;
     if (MP_OBJ_IS_TYPE(args[1], &mp_type_tuple)) {
       mp_obj_tuple_get(args[1], &xy_cnt, &xy_obj);
     } else {
@@ -541,7 +541,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_offset_obj, 1,
 ///     Saves current display contents to PNG file with given prefix.
 ///     """
 STATIC mp_obj_t mod_trezorui_Display_save(mp_obj_t self, mp_obj_t prefix) {
-  mp_buffer_info_t pfx;
+  mp_buffer_info_t pfx = {0};
   mp_get_buffer_raise(prefix, &pfx, MP_BUFFER_READ);
   if (pfx.len > 0) {
     display_save(pfx.buf);
diff --git a/core/embed/extmod/modtrezorutils/modtrezorutils.c b/core/embed/extmod/modtrezorutils/modtrezorutils.c
index 8c892671b..5537214cd 100644
--- a/core/embed/extmod/modtrezorutils/modtrezorutils.c
+++ b/core/embed/extmod/modtrezorutils/modtrezorutils.c
@@ -36,9 +36,9 @@
 ///     expected to avoid any invalid memory access.
 ///     """
 STATIC mp_obj_t mod_trezorutils_consteq(mp_obj_t sec, mp_obj_t pub) {
-  mp_buffer_info_t secbuf;
+  mp_buffer_info_t secbuf = {0};
   mp_get_buffer_raise(sec, &secbuf, MP_BUFFER_READ);
-  mp_buffer_info_t pubbuf;
+  mp_buffer_info_t pubbuf = {0};
   mp_get_buffer_raise(pub, &pubbuf, MP_BUFFER_READ);
 
   size_t diff = secbuf.len - pubbuf.len;
@@ -73,11 +73,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorutils_consteq_obj,
 STATIC mp_obj_t mod_trezorutils_memcpy(size_t n_args, const mp_obj_t *args) {
   mp_arg_check_num(n_args, 0, 4, 5, false);
 
-  mp_buffer_info_t dst;
+  mp_buffer_info_t dst = {0};
   mp_get_buffer_raise(args[0], &dst, MP_BUFFER_WRITE);
   uint32_t dst_ofs = trezor_obj_get_uint(args[1]);
 
-  mp_buffer_info_t src;
+  mp_buffer_info_t src = {0};
   mp_get_buffer_raise(args[2], &src, MP_BUFFER_READ);
   uint32_t src_ofs = trezor_obj_get_uint(args[3]);
 
@@ -104,7 +104,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorutils_memcpy_obj, 4, 5,
 ///     Halts execution.
 ///     """
 STATIC mp_obj_t mod_trezorutils_halt(size_t n_args, const mp_obj_t *args) {
-  mp_buffer_info_t msg;
+  mp_buffer_info_t msg = {0};
   if (n_args > 0 && mp_get_buffer(args[0], &msg, MP_BUFFER_READ)) {
     ensure(secfalse, msg.buf);
   } else {