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iDEFENSE Security Advisory 12.16.04: MPlayer Bitmap Parsing Remote Heap Overflow Vulnerability

MPlayer Bitmap Parsing Remote Heap Overflow VulnerabilityiDEFENSE Security Advisory 12.16.04http://www.idefense.com/application/poi/display?id=168December 16, 2004I. BACKGROUNDMPlayer is a movie player for Linux that also runs on many other Unices, and non- x86 CPUs. It plays most MPEG, VOB, AVI, Ogg/OGM, VIVO, ASF/WMA/WMV, QT/MOV/MP4, FLI, RM, NuppelVideo, YUV4MPEG, FILM, RoQ, PVA files, supported by many native, XAnim, and Win32 DLL codecs. You can watch VideoCD, SVCD, DVD, 3ivx, DivX 3/4/5 and other formats. More information is available athttp://mplayerhq.hu/.II. DESCRIPTIONRemote exploitation of a heap overflow vulnerability in Unix MPlayer could allow attackers to gain access to the computer. The vulnerability specifically exists due to a lack of bounds checking within the demux_open_bmp() routine defined in /libmpdemux/demux_bmp.c. If a specially crafted file specifies a large value for the "biClrUsed" field, an overflow is triggered in stream_read(). The vulnerable portion of code is displayed here: demuxer_t* demux_open_bmp(demuxer_t* demuxer){    sh_video_t *sh_video = NULL;    unsigned int filesize;    unsigned int data_offset;    bmp_image_t *bmp_image;    ...    sh_video->bih->biClrUsed = stream_read_dword_le(demuxer->stream);    sh_video->bih->biClrImportant = stream_read_dword_le(demuxer->stream);    // fetch the palette[!]  stream_read(demuxer->stream, (unsigned char *)(sh_video->bih) + 40,    sh_video->bih->biClrUsed * 4);    ...} In the given example call to stream_read(), an unchecked amount of data as specified by "biClrUsed" will be read into the fixed size buffer "bih." This allows control of execution by overwriting the saved return address on the stack.III. ANALYSISSuccessful exploitation of this vulnerability allows remote attackers to execute arbitrary code under the privileges of the user who attempted to view the bitmap file. Exploitation is not trivial, as a high level of precision is required. It is not a requirement for the malicious file to have an extension of .bmp because MPlayer will correctly determine if it is a bitmap file despite its extension.IV. DETECTIONiDEFENSE has confirmed that MPlayer version 1.0pre5 is vulnerable.The following distributions of Linux include MPlayer:                Debian Linux         Fedora Linux         Gentoo Linux         SUSE Linux V. WORKAROUNDUsers must be careful when accepting and opening media from untrusted sources.VI. VENDOR RESPONSEA patch to address this vulnerability is available at:http://www1.mplayerhq.hu/MPlayer/patches/bmp_fix_20041215.diffVII. CVE INFORMATIONA Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has notbeen assigned yet.VIII. DISCLOSURE TIMELINE12/10/2004  Initial vendor notification12/16/2004  Public disclosureIX. CREDITThe discoverer of this vulnerability wishes to remain anonymous.Get paid for vulnerability researchhttp://www.idefense.com/poi/teams/vcp.jspX. LEGAL NOTICESCopyright © 2004 iDEFENSE, Inc.Permission is granted for the redistribution of this alertelectronically. It may not be edited in any way without the expresswritten consent of iDEFENSE. If you wish to reprint the whole or anypart of this alert in any other medium other than electronically, pleaseemail customerservice () idefense com for permission.Disclaimer: The information in the advisory is believed to be accurateat the time of publishing based on currently available information. Useof the information constitutes acceptance for use in an AS IS condition.There are no warranties with regard to this information. Neither theauthor nor the publisher accepts any liability for any direct, indirect,or consequential loss or damage arising from use of, or reliance on,this information.

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