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         Technical Cyber Security Alert TA04-356A 
    Exploitation of phpBB highlight parameter vulnerability

   Original release date: December 21, 2004
   Last revised: --
   Source: US-CERT

Systems Affected

   phpBB versions 2.0.10 and prior

Overview

   The software phpBB contains an input validation problem in how it
   processes a parameter contained in URLs. An intruder can deface a
   phpBB website, execute arbitrary commands, or gain administrative
   privileges on a compromised bulletin board.

I. Description

   phpBB is an open-source bulletin board application. It fails to
   properly perform an urldecode() on the "highlight" parameter supplied
   to viewtopic.php. This may allow a remote attacker to execute
   arbitrary commands on a vulnerable server.

   According to reports, this vulnerability is being actively exploited
   by the Santy.A worm. The worm appears to propogate by searching for
   the keyword "viewtopic.php" in order to find vulnerable sites.

   The worm writes itself to a file named "m1ho2of" on the compromised
   system. It then overwrites files ending with .htm, .php, .asp. shtm,
   .jsp, and .phtm replacing them with HTML content that defaces the web
   page. The worm then tries to use PERL to execute itself on the
   compromised system and propogate further.
   US-CERT is tracking this issue as:

   VU#497400 - phpBB viewtopic.php fails to properly sanitize input
   passed to the "highlight" parameter

II. Impact

   A remote attacker may be able to deface a phpBB website and execute
   arbitrary commands on a compromised bulletin board.

III. Solution

Upgrade phpBB

   Upgrade to phpBB verison 2.0.11 to prevent exploitation.

Appendix A. References

     * US-CERT Vulnerability Note VU#497400 - 
       <http://www.kb.cert.org/vuls/id/497400>
     * phpBB Downloads - < http://www.phpbb.com/downloads.php>
     * phpBB Announcement - 
       <http://www.phpbb.com/phpBB/viewtopic.php?f=14&t=240636>
     * Symantec Security Response - Perl.Santy - 
       <http://securityresponse.symantec.com/avcenter/venc/data/perl.santy
       .html>
     * McAfee - Computer Virus Software and Internet Security -
       <http://us.mcafee.com/virusInfo/default.asp?id=description&virus_k=
       130471>
   _________________________________________________________________

   This vulnerability was reported by the phpBB Development Team.
   _________________________________________________________________

   Feedback can be directed to the authors: Jeffrey Gennari and 
   Jason Rafail
   _________________________________________________________________

   This document is available from:
   
      <http://www.us-cert.gov/cas/techalerts/TA04-356A.html>
   
   _________________________________________________________________

   Copyright 2004 Carnegie Mellon University.
   
   Terms of use: <http://www.us-cert.gov/legal.html>
   _________________________________________________________________

   Revision History

   Dec 21, 2004: Initial release

                      Last updated December 21, 2004 
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