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ICQ 6 Buffer Overflow Vulnerability
------------------------------------------------------------------------
SUMMARY
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".
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.
DETAILS
Vulnerable Systems:
* ICQ version 6 (build 6043)
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
Fix:
The vendor has addressed this vulnerability on 1st of March 2008 with an
automatic update.
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
ADDITIONAL INFORMATION
The information has been provided by <mailto:infocus@infigo.hr> infocus.
The original article can be found at:
<http://www.infigo.hr/en/in_focus/advisories/INFIGO-2008-04-08>
http://www.infigo.hr/en/in_focus/advisories/INFIGO-2008-04-08
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