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Trillian Remote DoS

daemon@ATHENA.MIT.EDU (flur)
Fri Jul 4 18:53:18 2003

Message-Id: <5.1.0.14.2.20030704180634.0421dba8@mail.tht.net>
Date: Fri, 04 Jul 2003 18:09:55 -0400
To: bugtraq Security List <bugtraq@securityfocus.com>
From: flur <flur@flurnet.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed

Application:    Trillian
Developer(s):   Cerulean Studios (http://www.trillian.cc)
Scope:          Remote DoS & Possible Exploit
Tested on:      Trillian 1.0 Pro, 0.74 Freeware

It is possible to crash Trillian by sending a corrupt 'TypingUser' message. 
Replacing any of the characters in 'TypingUser' will cause Trillian to 
crash. If more then 10 characters are used, or if the colon is omitted, 
Trillian will not crash. The crash occurs due to a function within msn.dll 
for both Trillian 1 and 0.74. This may be exploitable further.

In order to exploit this condition, no code is necessary- simply hex edit 
a  messenger client, replacing the string 'TypingUser' with any other 
string of the same length (or simply changing a letter or two). However 
this method of exploitation does break Microsoft's EULA/TOS, and you are 
not encouraged to utilize a broken client in this way except in an 
educational context. This 'hack' also prevents other non-trillian Messenger 
clients from detecting when a user is typing.

Crash Summary:

MOV ECX,DWORD PTR DS:[EDX]  ; EDX is uninitialized

The crash looks something like this:

Instruction at 0x####8826 referenced memory at 0x00000000

Sample TCP session to crash Trillian:

MIME-Version: 1.0
Content-Type: text/x-msmsgscontrol
TypingXxxx: attacker@blah.com

Our preliminary tests showed that memory was not manipulable, and thus this 
bug is not exploitable further then DoS. Please make further research 
public if you discover otherwise.




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