diff --git a/drivers/auth/mbedtls/mbedtls_crypto.c b/drivers/auth/mbedtls/mbedtls_crypto.c
index 178bbf5..42a0925 100644
--- a/drivers/auth/mbedtls/mbedtls_crypto.c
+++ b/drivers/auth/mbedtls/mbedtls_crypto.c
@@ -115,7 +115,7 @@
 	end = (unsigned char *)(p + sig_len);
 	signature.tag = *p;
 	rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len);
-	if (rc != 0) {
+	if ((rc != 0) || ((size_t)(end - p) != signature.len)) {
 		rc = CRYPTO_ERR_SIGNATURE;
 		goto end1;
 	}