Akeni LAN 1.2.118 Filter Bypass

`Title:  
======  
Akeni LAN v1.2.118 - Filter Bypass Vulnerability  
  
  
Date:  
=====  
2012-11-14  
  
  
References:  
===========  
http://www.vulnerability-lab.com/get_content.php?id=761  
  
  
VL-ID:  
=====  
761  
  
  
Common Vulnerability Scoring System:  
====================================  
3.3  
  
  
Introduction:  
=============  
Akeni LAN Messenger is an IM system designed for your LAN. It is easy to setup and does not requires a dedicated server   
or Internet connection. The rich client support chat, notification, conferencing, and file transfer. For those who also need   
authentication and encryption, please take a look at our Expert and Pro products.  
  
If your organization needs a web based solution that requires no client side installation of software, please take a look   
at our Web Chat. Due to the peer-to-peer nature of the product, there is no single point of failure and there is no need for   
any network setup. This make Akeni LAN Messenger a good solution for dynamic environment where two people can communicate with   
one another as long as the network itself is up and running. For example, LAN Messenger can be used by IT support personnel   
who needs a way to communicate and send files with each other anywhere in their network easily, without the need to connect   
to the Internet or to a centralized server.  
  
(Copy of the Vendor Website: http://www.akeni.com/en/product/lanmessenger.php )  
  
  
Abstract:  
=========  
The Vulnerability Laboratory Research Team discovered a filter bypass software vulnerability in the official Akeni LAN (LE) Messenger v1.2.118.  
  
  
Report-Timeline:  
================  
2012-11-14: Public or Non-Public Disclosure  
  
  
Status:  
========  
Published  
  
  
Exploitation-Technique:  
=======================  
Local  
  
  
Severity:  
=========  
Medium  
  
  
Details:  
========  
A filter bypass software vulnerability is the detected in the official Akeni LAN (LE) Messenger v1.2.118.  
The bug allows local attackers to inject own malicious persistent script codes on application-side.  
The vulnerability is located in the Akeni `incorrect length` exception-handling module with the bound vulnerable   
groupname (Gruppenname) parameter. The filter of the Akeni LAN Messenger santizes malicious tags and evil frame   
context but does not recognize a secound splitted (%20) request after the first. The attacker can provoke a first   
parse by injecting for example a >`` to match the invalid exception criterias. After the provoke he splits the request   
with %20 and inject his own tags directly after it. The result is a persistent script code execution out of the invalid length &  
invalid parameter software exception-handling.  
  
Vulnerable Module(s):  
[+] Menu > Action > Contact List > Add Group  
  
Vulnerable Parameter(s):  
[+] Incorrect Length - Exception-Handling  
[+] Invalid Context - Exception-Handling  
  
  
Proof of Concept:  
=================  
The vulnerability can be exploited by local attackers without required user inter action. For demonstration or reproduce ...  
  
1.  
Let us watch the exception-handling of the invalid length. First we inject a standard iframe like >"<iframe src=a>  
  
[>"'>] has incorrect length.  
Groups name must have between %2 and %3 characters.  
  
... the validation of the incorrect length or invalid parameter redisplays the message but parse the iframe tag.  
We can see in the parse the >" which is splitted from the parse itself and shows is there could be an injection possibility.  
  
1.2  
The next step will be to split the request. HOW?! We inject a standard iframe (<iframe src=a>) split the request   
with %20 (Space) and inject the secound script code after the split.  
  
PoC:  
String: >"<iframe src=a><%20>"<img src=http://www.vulnerability-lab.com/gfx/logo-header.png>  
  
--- Exception Logs (Bypass) ---  
[>""] has incorrect length.   
Groups name must have between 30 and %3 characters.  
  
  
Risk:  
=====  
The security risk of the local persistent software vulnerability is estimated as medium(-).  
  
  
Credits:  
========  
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected])  
  
  
Disclaimer:  
===========  
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