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[SVRT-05-08] Critical BoF vulnerability found in ffdshow affecting all internet browsers (SVRT-Bkis)

1. General Information

ffdshow is a DirectShow filter and VFW codec for many audio and video formats, such as DivX, Xvid and H.264. It is the most popular audio and video decoder on Windows. Besides a stand-alone setup package, ffdshow is often included in almost all codec pack software such as K-lite Codec Pack, XP Codec Pack, Vista Codec Package, Codec Pack All in one,.

In Oct 2008, SVRT-Bkis has detected a serious buffer overflow vulnerability in ffdshow which affects all available internet browsers. Taking advantage of the flaw, hackers can perform remote attack, inject viruses, steal sensitive information and even take control of the victim's system.

Since ffdshow is an open source software (can be found at http://sourceforge.net/projects/ffdshow-tryout), we have contacted the developing team and they have patched the vulnerability in the latest version of ffdshow.

Details : http://security.bkis.vn/?p=277
SVRT Advisory  : SVRT-05-08
Initial vendor notification :  13-11-2008
Release Date : 24-11-2008
Update Date  : 24-11-2008
Discovered by : SVRT-Bkis
Security Rating :  Critical
Impact  Remote : Code Execution
Affected Software : ffdshow  (< rev2347 20081123)

2. Technique Description

The flaw occurs when ffdshow works with a media stream (e.g. http://[website]/test.avi). On parsing an overly long link, ffdshow would encounter a buffer overflow error as the memory is not allocated and controlled well.

ffdshow is in fact a codec component for decoding multimedia formats so it must be used via some media player; the default program is Windows Media Player (wmp). Due to this reason, all internet browsers that support wmp plug-in are influenced by this vulnerability, such as Internet Explorer, Firefox, Opera, Chrome...

In order to exploit, hackers trick users into visiting a website containing malicious code. If successful, malicious code would be executed without any users' further interaction. Hackers can then take complete control of the system.

3. Solution

As for the seriousness of the vulnerability, it has been patched in the latest version of ffdshow by the developing team of the software. Bkis Internetwork Security Center highly recommends that users should update ffdshow to the latest version here: http://sourceforge.net/project/showfiles.php?group_id=173941&package_id=199416&release_id=439904

At the moment, there are a lot of software packages packing ffdshow that haven't been updated. On account of this, users should also update the ffdshow latest versions:
- K-Lite Codec Pack (lastest version).
- XP Codec Pack (lastest version).
- Vista Codec Package (lastest version).
- Codec Pack All in one (lastest version).
- Storm Codec Pack (lastest version).
- And many other software Codec packages using ffdshow.

In addition, software producers that make use of ffdshow in their products should also update these products with the latest version of ffdshow.

4. Credits
Thanks Nguyen Anh Tai for working with SVRT-Bkis.

Bach Khoa Internetwork Security Center (BKIS)
Hanoi University of Technology (Vietnam)

Email : svrt@xxxxxxxxxxx
Website : www.bkav.com.vn
WebBlog : security.bkis.vn
Our PGP : http://security.bkis.vn/policy/pgp/SVRT-Bkis.gpg