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Category:   Application (Forum/Board/Portal)  >   YaBB Vendors:   YaBB Development Team
YaBB 'member.vars' File Lets Remote Users Gain Administrative Privileges
SecurityTracker Alert ID:  1018236
SecurityTracker URL:
CVE Reference:   CVE-2007-3208   (Links to External Site)
Updated:  May 11 2008
Original Entry Date:  Jun 13 2007
Impact:   Modification of user information, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.1
Description:   A vulnerability was reported in YaBB. A remote user can gain administrative access on the target application.

A remote user can send specially crafted data to inject a CR/LF character sequence and write to the user's 'vars' file to register an account with administrator privileges.

The vendor was notified on May 23, 2007.

Peter Vreugdenhil reported this vulnerability to iDefense.

Impact:   A remote user can gain administrative privileges on the target application.
Solution:   The vendor has issued a patch:

The YaBB advisory is available at:;action=display;num=1181678785

Vendor URL: (Links to External Site)
Cause:   Input validation error
Underlying OS:  Linux (Any), UNIX (Any), Windows (Any)

Message History:   None.

 Source Message Contents

Subject:  iDefense Security Advisory 06.12.07: YaBB Forum member.vars CRLF

YaBB Forum member.vars CRLF Injection Privilege Escalation Vulnerability

iDefense Security Advisory 06.12.07
Jun 12, 2007


YaBB (Yet another Bulletin Board) is an Open Source community forum
system written in Perl. More information is available at the following


Remote exploitation of an input validation error within version 2.1 of
YaBB Forum allows attackers to register with forum Administrator

The problem specifically exists due to insufficient validation when
writing to the "vars" file for each user. By setting the values of
certain variables to contain certain characters, attackers can elevate
their privileges to that of the forum Administrator.


Exploitation allows attackers to obtain Administrator privileges, which
include the ability to modify forum templates (i.e., Perl code). This
allows administrators to execute arbitrary commands in the context of
the web server running the forum.

This attack can be performed during registration. This allows
unauthenticated attackers to obtain forum Administrator privileges at
registration time via the script.

Additionally, once registered, a forum user can modify their profile and
conduct this attack using the script.


iDefense confirmed the existence of this vulnerability within version
2.1 of YaBB Forum.


Disabling the registration feature of the forum mitigates this issue.


The YaBB Forum team has addressed this vulnerability by releasing a
software update. For more information consult the following announce on
their home site.;action=display;num=1181678785


A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.


05/23/2007  Initial vendor notification
05/23/2007  Initial vendor response
06/12/2007  Coordinated public disclosure


This vulnerability was reported to iDefense by Peter Vreugdenhil.

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