========================================================================
= Winamp - Buffer Overflow In IN_CDDA.dll
=
= Vendor Update:  
= http://www.winamp.com/player/
=
= Affected Software:
=       Winamp 5.05 (only version tested)
=
= Public disclosure on November 23, 2004
========================================================================

== Overview ==

In this time of responsible vulnerability disclosure, it's a little
disturbing when a vendor acts on disclosed information but gives no
recognition or even notification that an update has been created due to
the information passed to them.

This advisory is a little late, the update was posted to the vendor
website last week. The only reason I know this, is because I asked and
received a response.
------------------------------------------------------------------------

hi brett

the problem was fixed in the lastest [sic] release of winamp.  
version 5.06 went live on the site last thurday [sic].

thanks

jonathan ward

------------------------------------------------------------------------

But enough of that, we know the game and still choose to play.

We discovered a remotely exploitable stack based buffer overflow in 
winamp version 5.05. It is possible that earlier versions are also
vulnerable and we recommend all users to upgrade to the latest version.

The overflow can be caused in various ways, the most dangerous though is
through a malformed .m3u playlist file. When hosted on a web site, these
files will automatically downloaded and open in winamp without any user
interaction. This is enough to cause the overflow that would allow a 
malicious playlist to overwrite EIP and execute arbitrary code.

== Exploitation ==

When winamp opens the malformed playlist file, a first exception will 
occur: 

First Chance Exception in winamp.exe (IN_CDDA.DLL) : Access Violation
At this location
00A49BE8 88 4C 04 30          mov         byte ptr [esp+eax+30h],cl

This exception will be handled by winamp, and execution will then 
continue until it reaches the second exception at this location
61616161   ???

with the registers looking like;
EAX = 0012A5D8 EBX = 0012C024
ECX = 61616161 EDX = 77F96DAE
ESI = 0012A600 EDI = 0046B9E0
EIP = 61616161 ESP = 0012A540
EBP = 0012A560 EFL = 00210246

As can be seen, EIP has been overwritten with a value supplied through
the malformed playlist file, 0x61616161 (aaaa) and since more playlist
supplied data is located at the address pointed to by EDI, execution of
malicious code is possible.

== Solutions ==

- Install the vendor supplied patch.

== Credit ==

Discovered and advised to Nullsoft October 14, 2004 by Brett Moore of
Security-Assessment.com

== About Security-Assessment.com ==

Security-Assessment.com is a leader in intrusion testing and security
code review, and leads the world with SA-ISO, online ISO17799 compliance
management solution. Security-Assessment.com is committed to security
research and development, and its team have previously identified a
number of vulnerabilities in public and private software vendors products.

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