diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/IXR/class-IXR-message.php
--- a/wp/wp-includes/IXR/class-IXR-message.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/IXR/class-IXR-message.php	Tue Dec 15 13:49:49 2020 +0100
@@ -110,20 +110,28 @@
         $chunk_size = apply_filters( 'xmlrpc_chunk_parsing_size', $chunk_size );
 
         $final = false;
+
         do {
             if (strlen($this->message) <= $chunk_size) {
                 $final = true;
             }
+
             $part = substr($this->message, 0, $chunk_size);
             $this->message = substr($this->message, $chunk_size);
+
             if (!xml_parse($this->_parser, $part, $final)) {
+                xml_parser_free($this->_parser);
+                unset($this->_parser);
                 return false;
             }
+
             if ($final) {
                 break;
             }
         } while (true);
+
         xml_parser_free($this->_parser);
+        unset($this->_parser);
 
         // Grab the error messages, if any
         if ($this->messageType == 'fault') {