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             AUSCERT External Security Bulletin Redistribution

           ESB-2004.0787 -- iDEFENSE Security Advisory 12.16.04
            MPlayer MMST Streaming Stack Overflow Vulnerability
                             17 December 2004

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           MPlayer
Publisher:         iDEFENSE
Operating System:  Linux variants
                   UNIX variants
Impact:            Execute Arbitrary Code/Commands
Access:            Remote/Unauthenticated

Ref:               ESB-2004.0786

Original Bulletin: http://www.idefense.com/application/poi/display?id=167

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MPlayer MMST Streaming Stack Overflow Vulnerability

iDEFENSE Security Advisory 12.16.04
http://www.idefense.com/application/poi/display?id=167
December 16, 2004

I. BACKGROUND

MPlayer 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 at http://mplayerhq.hu/.

II. DESCRIPTION

Remote exploitation of a stack overflow vulnerability in MPlayer could 
allow remote users to gain access to the computer.

The vulnerability specifically exists due to a lack of bounds checking 
in /libmpdemux/asf_mmst_straming.c. If a specially crafted file 
specifies a large value for the length field, the overflow is triggered 
in get_data(). The vulnerable code follows: 

static int get_media_packet (int s, int padding, streaming_ctrl_t
*stream_ctrl) {
  unsigned char  pre_header[8];
  char           data[BUF_SIZE];
  
[...]
    packet_len = get_32 ((unsigned char*)&packet_len, 0) + 4;

[!]    if (!get_data (s, data, packet_len)) {
      printf ("command data read failed\n");
      return 0;
    }
[...] 

Once the get_data function overwrites stack memory, the saved return 
address can be controlled, thus allowing for execution of arbitrary 
code.

III. ANALYSIS

If remote exploitation is successful, the attacker would be able to gain

access with the privileges of the user who attempted to view the stream.

IV. DETECTION

iDEFENSE 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. WORKAROUND

Users must be careful when accepting and opening media from untrusted 
sources. Do not accept media from those you do not trust. Do not stream 
media from servers you do not trust.

VI. VENDOR RESPONSE

A patch to address this vulnerability is available at:

http://www1.mplayerhq.hu/MPlayer/patches/mmst_fix_20041215.diff

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/10/2004  Initial vendor notification
12/16/2004  Public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp

X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author 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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