INFIGO IS Security Advisory #ADV-2008-04-08
              http://www.infigo.hr/en/



Title: ICQ 6 remote buffer overflow vulnerability
Advisory ID: INFIGO-2008-04-08
Date: 2008-04-14
Advisory URL: http://www.infigo.hr/en/in_focus/advisories/INFIGO-2008-04-08
Impact: Remote code execution
Risk Level: High
Vulnerability Type: Remote


==[ Overview
 
ICQ (I Seek You) Instant Messenger is one of the most popular internet 
chat software. Since 1996, it has grown to a community of over 180 
million users. It has features for instant messaging, chat, sending 
e-mail, SMS, file transfer, wireless-pager messages, etc. 


==[ Vulnerability

INFIGO IS's security team identified a critical remote buffer overflow 
vulnerability in the latest ICQ version (ICQ 6.0). In newer versions, 
ICQ has a 'Personal Status Manager' feature, where a user can specify 
text messages for his status/mood (online/offline/etc.). The specified 
message will be visible in the title part of a remote user's ICQ chat 
window, when a chat session is initiated. 

When a user writes a message in the status manager, the text string is 
processed with the boxelyRenderer module. The boxelyRenderer module has 
a vulnerability in the HTML tags processing code. If malformed HTML tags 
are set for the 'status message', boxelyRenderer will try to process the 
HTML tags, and a UNICODE heap overflow will occur. 

The 'status' string from a remote user is processed by boxelyRenderer 
for each new chat session. If the remote user has a malicious 'status 
message', ICQ's heap memory will be overflowed. 

Upon setting, the status message is sent to ICQ's servers, and will be 
stored on them. When another user looks up the malicious user's profile, 
or tries to send him a message, even if the malicious user is offline, 
the ICQ client will receive the malicious status message from ICQ's 
server. In other words, once the malicious user sets his status message, 
he doesn't have to be online in order to exploit other vulnerable ICQ 
clients. 

There are few different exploitation paths for this vulnerability, and 
they depend on user actions in ICQ and the current heap state. 

Below is an example of malicious HTML code that will crash ICQ:
 
------
|<a href="AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"><img
src="AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" border="0" /></a>|
------
 
When a user sets this HTML code as his 'status message', 
ICQ/boxelyRenderer will process it and ICQ will crash. To prevent this, 
open ICQ in debugger and set it to ignore INT3 and memory violation 
exceptions. 

We identified two exploitable scenarios:

Scenario 1: 

In this scenario, the ESI register has our input, so we control the EIP 
register at the 'CALL' instruction. 

boxelyRE:
------
MOV EDX, DWORD PTR DS:[ESI]
PUSH 5A
LEA EAX, DWORD PTR SS:[EBP-2A0]
PUSH EAX
MOV ECX, ESI
CALL DWORD PTR DS:[EDX+8] <- HERE
-------
 
Scenario 2:

In this scenario, which is harder to exploit, we can write one byte to a 
memory location. 
 
ntdll:
-------
MOV BYTE PTR DS:[EDI+6], AL
-------
 
 
==[ Affected Version
 
The vulnerability has been identified in the latest available ICQ 
version 6 (build 6043). It was tested on Windows XP SP2 and Windows 
2003. 


==[ Fix
 
The vendor has addressed this vulnerability on 1st of March 2008 with an 
automatic update. 


==[ PoC Exploit
 
PoC will not be released.
 
 
==[ Vendor status
 
26.02.2008 - Initial contact
26.02.2008 - Initial vendor response
28.02.2008 - Further clarification about the vulnerability
28.02.2008 - Vendor status update
01.03.2008 - Vendor released an automatic update.
14.03.2008 - Vendor status update
14.04.2008 - Coordinated public disclosure
 
 
==[ Credits
 
Vulnerability discovered by Leon Juranic <leon.juranic@infigo.hr>. 
Special thanks to Marko Goricki, who pointed on the ICQ crash :-). 

 
==[ INFIGO IS Security Contact
 
INFIGO IS,
 
WWW : http://www.infigo.hr/en/
E-mail : infocus@infigo.hr