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Advisory: VLC media player RealMedia Processing Integer
Overflow Vulnerability
Advisory ID: TKADV2008-013
Revision: 1.0
Release Date: 2008/11/30
Last Modified: 2008/11/30
Date Reported: 2008/11/14
Author: Tobias Klein (tk at trapkit.de)
Affected Software: VLC media player < 0.9.7
Remotely Exploitable: Yes
Locally Exploitable: No
Vendor URL: http://www.videolan.org/
Vendor Status: Vendor has released an updated version
CVE-ID: CVE-2008-5276
Patch development time: 16 days
======================
Vulnerability Details:
======================
The VLC media player contains an integer overflow vulnerability while
parsing malformed RealMedia (.rm) files. The vulnerability leads to a
heap
overflow that can be exploited by a (remote) attacker to execute
arbitrary
code in the context of VLC media player.
==================
Technical Details:
==================
Source code file: modules\demux\real.c
[...]
891 static void ReadRealIndex( demux_t *p_demux )
892 {
...
900 uint32_t i_index_count;
...
920 [1] i_index_count = GetDWBE( &buffer[10] );
...
931 [2] p_sys->p_index =
932 (rm_index_t *)malloc( sizeof( rm_index_t ) *
(i_index_count+1) );
933 if( p_sys->p_index == NULL )
934 return;
935
936 memset(p_sys->p_index, 0, sizeof(rm_index_t) *
(i_index_count+1));
937
938 [3] for( i=0; i<i_index_count; i++ )
939 {
940 if( stream_Read( p_demux->s, buffer, 14 ) < 14 )
941 return ;
942
943 [7] if( GetWBE( &buffer[0] ) != 0 )
944 {
945 msg_Dbg( p_demux, "Real Index: invaild version of index
entry %d ",
946 GetWBE( &buffer[0] ) );
947 return;
948 }
949
950 [4] p_sys->p_index[i].time_offset = GetDWBE( &buffer[2] );
951 [5] p_sys->p_index[i].file_offset = GetDWBE( &buffer[6] );
952 [6] p_sys->p_index[i].frame_index = GetDWBE( &buffer[10] );
953 msg_Dbg( p_demux, "Real Index: time %d file %d frame %d ",
954 p_sys->p_index[i].time_offset,
955 p_sys->p_index[i].file_offset,
956 p_sys->p_index[i].frame_index );
957
958 }
959 }
[...]
[1] User supplied data from the RealMedia file gets copied into
"i_index_count".
[2] The value of "i_index_count" is used to calculate the size of a heap
buffer. If the value of "i_index_count" is big enough (e.g.
0x15555555)
an integer overflow occurs while calculating the size of the heap
buffer. As a consequence it is possible to allocate a small heap
buffer
by supplying a big value for "i_index_count".
[3] The value of "i_index_count" is used as a counter in this for()
loop.
[4] User controlled data from the RealMedia file gets copied into the
previously allocated heap buffer (see [2]). As "i" is used as an
array
index and the for() loop is executed until "i<i_index_count" it is
possible to overflow the heap buffer with user controlled data from
the
RealMedia file.
[5] See [4]
[6] See [4]
As there is also an exit condition that can be triggered to stop the
overflow (see [7]) at any given point this leads to a fully controllable
heap overflow that can be exploited by a (remote) attacker to execute
arbitrary code in the context of VLC.
=========
Solution:
=========
See "Workarounds" and "Solution" sections of the VideoLAN-SA-0811 [1].
========
History:
========
2008/11/14 - Vendor notified
2008/11/17 - Patch developed by VideoLAN team
2008/11/30 - Public disclosure of vulnerability details by the vendor
2008/11/30 - Release date of this security advisory
========
Credits:
========
Vulnerability found and advisory written by Tobias Klein.
===========
References:
===========
[1] http://www.videolan.org/security/sa0811.html
[2] http://git.videolan.org/?p=vlc.git;a=commitdiff;h=d19de4e9f2211cbe5
bde00726b66c47a424f4e07
[3] http://www.trapkit.de/advisories/TKADV2008-013.txt
========
Changes:
========
Revision 0.1 - Initial draft release to the vendor
Revision 1.0 - Public release
===========
Disclaimer:
===========
The information within this advisory may change without notice. Use
of this information constitutes acceptance for use in an AS IS
condition. There are no warranties, implied or express, with regard
to this information. In no event shall the author be liable for any
direct or indirect damages whatsoever arising out of or in connection
with the use or spread of this information. Any use of this
information is at the user's own risk.
==================
PGP Signature Key:
==================
http://www.trapkit.de/advisories/tk-advisories-signature-key.asc
Copyright 2008 Tobias Klein. All rights reserved.
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