diff --git a/library/x509_crt.c b/library/x509_crt.c
index dfd22f6..0287b5b 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -891,6 +891,9 @@
     size_t len;
     unsigned char *end_ext_data, *end_ext_octet;
 
+    if( *p == end )
+        return( 0 );
+
     if( ( ret = mbedtls_x509_get_ext( p, end, &crt->v3_ext, 3 ) ) != 0 )
     {
         if( ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
@@ -899,6 +902,7 @@
         return( ret );
     }
 
+    end = crt->v3_ext.p + crt->v3_ext.len;
     while( *p < end )
     {
         /*