XennoBB <= "avatar gallery" Directory Transversal

--------------------- SUMMARY ---------------------

Name:

XennoBB "avatar gallery" directory transversal (10/8/2006)

Vendor / Product:

XennoBB Group

http://www.xennobb.com/

Description:

The world's most revolutionary and easy to use bulletin board.

Revolutionary because it redefines the boundaries of usability

and power; from the first version it's a real alternative to

the commercial forums out there.

How can XennoBB be described in few words?

Lightning-speed, stable, SECURED(?) and modern.

Version(s) Affected:

<= 2.1.0

Severity:

Medium

Impact:

Directory transversal (Remote)

Status:

Unpatched

Discovered by:

Chris Boulton <http://www.surfionline.com>

Original advisory:

http://www.surfionline.com/security_advisories/20060810_xennobb_avatar_g
allery_transversal.txt

------------------- DESCRIPTION -------------------

An exploit exists in the above mentioned versions of XennoBB which

can be exploited by malicious users to transverse various directories

on the server.

Input passed to the "gallery" parameter in profile.php is not properly

sanitized before being used to open the corresponding directory on the

file system. This exploit can lead to manipulation of content in higher

up directories than the script intends.

--------------------- EXPLOIT ---------------------

Submit a forged POST request to

profile.php?action=avatar_gallery&id={your registered user ID here}

With the following as the POST data:

category=../../general/

Successful exploitation leads to images in the /img/general folder

being shown to the user. A similar process can be used to obtain other

confidential system documents or images which may exist on the server.

--------------------- SOLUTION --------------------

Ensure input is correctly sanitized and invalid/not acceptable

characters are removed from the gallery POST variable before the

directory is opened on the server.

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