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Advisory 18/2005: PHP Cross Site Scripting (XSS) Vulnerability in phpinfo()
From: Stefan Esser <sesser () hardened-php net>
Date: Mon, 31 Oct 2005 14:33:22 +0100

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                        Hardened-PHP Project
                        www.hardened-php.net

                      -= Security  Advisory =-


     Advisory: PHP Cross Site Scripting (XSS) Vulnerability in phpinfo()
 Release Date: 2005/10/31
Last Modified: 2005/10/31
       Author: Stefan Esser [sesser () hardened-php net]

  Application: PHP4 <= 4.4.0
               PHP5 <= 5.0.5
     Severity: A Cross Site Scripting (XSS) Vulnerability in phpinfo()
               could f.e. lead to cookie data exposure if an info
               script is left on a production server.
         Risk: Low
Vendor Status: Vendor has released a bugfixed PHP 4 version
   References: http://www.hardened-php.net/advisory_182005.77.html


Overview:

   PHP is a widely-used general-purpose scripting language that is
   especially suited for Web development and can be embedded into HTML.

   During the development of the Hardening-Patch which adds security 
   hardening features to the PHP codebase, several vulnerabilities 
   within PHP were discovered. This advisory describes one of these 
   flaws concerning a weakness in the phpinfo() function, which allows
   Cross Site Scripting (XSS).


Details:
   
   The phpinfo() function outputs a large amount of information about 
   the current state of PHP. This includes information about PHP 
   compilation options and extensions, the PHP version, server 
   information and environment (if compiled as a module), the PHP 
   environment, OS version information, paths, master and local 
   values of configuration options and request variables, HTTP 
   headers, and the PHP License.
   
   Because phpinfo() leaks a lot of information to the viewer it is
   not recommended to leave a script executing phpinfo() on a 
   production server. However in reality phpinfo() scripts are left
   open on a lot of servers. While this is already bad enough, there
   is also a problem when request variables of a certain form are
   displayed. With a properly crafted URL, that contains a stacked
   array assignment it is f.e. possible to inject HTML code into the 
   output of phpinfo(), which could result in the leakage of domain 
   cookies (f.e. session identifiers).


Proof of Concept:

   The Hardened-PHP project is not going to release exploits for any
   of these vulnerabilities to the public.


Recommendation:

   It is strongly recommended to never leave phpinfo() scripts on
   production servers, additionally it is recommended to upgrade to 
   the new PHP-Releases as soon as possible, because it also fixes 
   a few vulnerabilities, that are rated critical. Finally we always 
   recommend to run PHP with the Hardening-Patch applied.


GPG-Key:

   http://www.hardened-php.net/hardened-php-signature-key.asc

   pub  1024D/0A864AA1 2004-04-17 Hardened-PHP Signature Key
   Key fingerprint = 066F A6D0 E57E 9936 9082  7E52 4439 14CC 0A86 4AA1


Copyright 2005 Stefan Esser. All rights reserved.

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