[UNIX] YaBB Forum member.vars CRLF Injection Privilege Escalation Vulnerability

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YaBB Forum member.vars CRLF Injection Privilege Escalation Vulnerability
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SUMMARY

<http://www.yabbforum.com/> YaBB (Yet another Bulletin Board) is "an Open
Source community forum system written in Perl". Remote exploitation of an
input validation error within version 2.1 of YaBB Forum allows attackers
to register with forum Administrator privileges.

DETAILS

Vulnerable Systems:
* YaBB Forum version 2.1

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.

Analysis:
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 register.pl script.

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

Workaround:
Disabling the registration feature of the forum mitigates this issue.

Vendor response:
The YaBB Forum team has addressed this vulnerability by releasing a
software update. For more information consult the following announce on
their home site.

<http://www.yabbforum.com/community/?board=general;action=display;num=1181678785> http://www.yabbforum.com/community/?board=general;action=display;num=1181678785

Disclosure Timeline:
05/23/2007 - Initial vendor notification
05/23/2007 - Initial vendor response
06/12/2007 - Coordinated public disclosure

ADDITIONAL INFORMATION

The information has been provided by
<mailto:idlabs-advisories@idefense.com> iDefense Labs Security Advisories.
The original article can be found at:
<http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=538>

http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=538

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