Title:
======
Skype 5.3.x 2.2.x 5.2.x - Persistent Software Vulnerability


Date:
=====
2011-09-06



VL-ID:
=====
182


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 persistent software vulnerability in the main module of the Skype software.
The vulnerability is OS independent & has been successfully reproduced by the skype security team on windows7, macos and linux.


Report-Timeline:
================
2011-07-07:  Vendor Notification
2011-07-09:  Vendor Response/Feedback
2011-08-01:  Vendor Fix/Patch
2011-09-06:  Public or Non-Public Disclosure



Status:
========
Published


Affected Products:
==================
Microsoft
Product: Skype v5.3.x 2.2.x 5.2.x


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


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


Details:
========
An input validation vulnerability is detected on the windows, linux & macosx version of skype. The bug is located in the status bar 
module of the message index. The vulnerability allows an local attacker to implement persistent malicious script codes on a skype 
software main module. The successfully exploitation can lead to redirects, client exploitation, session hijacking, malicious downloads 
& request manipulation over the vulnerable software main module.

Vulnerable Module(s):
                [+] Status Message Index - Username Output

Exploited via:
                [+] Skype Manager Service


Verified on OS:
                [+] Windows 
                [+] MacOS
                [+] Linux


Affected OS version(s):
                Windows v5.3.0.120 & older versions
                MacOS v5.2.0.1523 & older versions
                Ubuntu v2.2.0.35 & older versions
                Debian v2.2.0.35-1 & older versions
                Fedora v2.2.0.35-f & older versions
                Suse v2.2.0.35-s & older versions

Pictures:
                ../1.png
                ../2.png


Solution:
=========
Validate the user name on the software status message output index on the main module.
Restrict the entry/input of malicious tags on bound services like skype manager.

Vendor Fix/Patch - 2011-08-12


Risk:
=====
The security risk of the persistent software vulnerability is estimated as high because it is located on a main module of the software client.


Credits:
========
Vulnerability Research Laboratory - Benjamin Kunz Mejri (Rem0ve)


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-
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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 
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