diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index e4b2c99..84f2f3d 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -2659,6 +2659,13 @@
     buf = ssl->in_msg;
 
     /* certificate_types */
+    if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
+        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+                                        MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
+        return( MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST );
+    }
     cert_type_len = buf[mbedtls_ssl_hs_hdr_len( ssl )];
     n = cert_type_len;