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ASX Playlists and Jumping to Conclusions
From: Sûnnet Beskerming <info () beskerming com>
Date: Fri, 8 Dec 2006 17:23:02 +1030

Hi list(s),

The recent coverage of ASX Playlist issues seems somewhat strange. For the uninitiated, here is a quick wrapup:

XMPlay ASX buffer overflow PoC code posted to milw0rm - 21 November

This PoC demonstrated an exploitable buffer overflow condition in the handling of 'ref href' URIs. A CVE entry (CVE-2006-6063 - though this only identifies the .m3u method of exploiting the vulnerability) appears around the same time, and reporting is carried by the usual third parties. With no fix present, this remains an effective 0-day (plus, with existing malware targeting .asx files it could make for interesting real-world use).

Windows Media Player DoS code posted to BugTraq - 22 November

Oddly, this code represented an almost exact duplicate of the buffer overflow demonstrated the day before, only with the exploit payload removed and replaced with a bunch of 'A's, and fails to draw much interest from third parties. It isn't until eEye publishes data on this issue (and increases the perceived threat posed) on their 0-day reporting / information site that it attracts some attention from other reporting parties (such as FrSIRT on 7 December), though uptake is slow.

Leaving Chinese Soup's critique (BugTraq) of eEye's analysis aside (why they haven't identified on the XMPlay vulnerability is another question), users need to be aware that if they replace WMP with XMPlay as the default handler of .asx content, then they are potentially creating a much riskier environment than if they accept the current DoS risk against their platform.

If this particular code release had appropriate accompanying documentation, it would be possible to work out whether it is a derivative of the earlier code, or fortuitous timing on something found independently.

Criticism has been recently levelled against third party reporting bodies for failing to adequately investigate reports (after one of the recent MoKB OS X corrupted .dmg file handling errors), and the way that information is flowing between, and being distributed by, third party reporting bodies in this case is showing similar patterns.

In summary:
- There is a known 0-day targeting a vulnerability in XMPlay's handling of malicious .asx (and other content types) data passed via 'ref href' that can lead to arbitrary code execution. - There is a known DoS targeting WMP that is exploited via a long string passed via 'ref href' and using the .asx media type
 - There has been no proven link between the two disclosures
- It has yet to be shown that the WMP vulnerability leads to arbitrary code execution - The advice to replace WMP as the default .asx filetype handler can lead to an increased security risk if the replacement application is XMPlay (accepting arbitrary code execution in an effort to avoid a DoS).


Carl Jongsma
info () beskerming com
Sûnnet Beskerming Pty. Ltd.
Adelaide, Australia

Sûnnet Beskerming Pty. Ltd.

Established in mid 2004, Sûnnet Beskerming Pty. Ltd. is the sister company to Jongsma & Jongsma Pty. Ltd., and was formed to develop and commercialise advanced Information Security research. Sûnnet Beskerming Pty. Ltd. is an Information Security specialist and, in conjunction with the tools developed in house, provides total security solutions and services, from the perimeter to internal data stores, including web application security and security testing and analysis.

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