diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index c80765b211cf0..029f7051f2bea 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -408,6 +408,8 @@ int x509_extract_key_data(void *context, size_t hdrlen,
 	ctx->cert->pub->pkey_algo = "rsa";
 
 	/* Discard the BIT STRING metadata */
+	if (vlen < 1 || *(const u8 *)value != 0)
+		return -EBADMSG;
 	ctx->key = value + 1;
 	ctx->key_size = vlen - 1;
 	return 0;