GOM Encoder Heap-based Buffer Overflow 1. General Information GOM Encoder is a video transcoder that can work with a lot of video formats. One of its functions is embedding subtitles to the video, which means you can see subtitles on the resulting video even if your device doesn't support subtitle. Bkis has just found a vulnerability in the software, related to the processing of subtitle files in "srt" format. Taking advantage of the flaw, hackers can perform denial of service attack or, if successfully exploit, remote code execution. We have sent the report to the vendor. Details : http://security.bkis.vn/?p=352 SVRT Advisory: Bkis-04-2009 Initial vendor notification: 03/04/2009 Release Date : 03/16/2009 Update Date : 03/16/2009 Discovered by : Mai Xuan Cuong, Bkis Attack Type : Buffer Overflow Security Rating : High Impact : Code Execution Affected Software : GOM Encoder Demo <= 1.0.0.11 2. Technical Description The vulnerability is related to the processing of subtitle files in "srt" format when transcoding videos with subtitle embedded. More precisely, it pops up when the program handles Preview/ Set Segment function. If the accompanied "srt" file has an overly long text field, it will cause a heap-based overflow, which in turn corrupts the memory and makes the program crash. To take advantage of the flaw, a hacker might create a specially crafted "srt" file and trick users into downloading it. If users use this file when transcoding videos with GOM Encoder, they will become victims of hacker. If successful, the hacker might execute arbitrary code within the context of the affected application. Failed exploitation results in a crash of the program, which might be used to perform Denial of Service attack. 3. Solution Rating this vulnerability high severity, Bkis recommends that users be cautious with "srt" files from untrustworthy sources until the vendor release the patch. Bkis