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 (at) bkav.com (dot) vn [email concealed] Website : www.bkav.com.vn WebBlog : security.bkis.vn Our PGP : http://security.bkis.vn/policy/pgp/SVRT-Bkis.gpg ----------------------------------------------------------------