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Subject: CERT Advisory CA-2002-21 Vulnerability in PHP
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-----BEGIN PGP SIGNED MESSAGE-----

CERT Advisory CA-2002-21 Vulnerability in PHP

   Original release date: July 22, 2002
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

     * Systems running PHP versions 4.2.0 or 4.2.1

Overview

   A  vulnerability  has been discovered in PHP. This vulnerability could
   be  used  by  a remote attacker to execute arbitrary code or crash PHP
   and/or the web server.

I. Description

   PHP  is  a  popular  scripting  language  in  widespread use. For more
   information about PHP, see

          http://www.php.net/manual/en/faq.general.php

   The  vulnerability  occurs  in the portion of PHP code responsible for
   handling  file uploads, specifically multipart/form-data. By sending a
   specially  crafted  POST  request  to  the web server, an attacker can
   corrupt  the  internal  data  structures used by PHP. Specifically, an
   intruder  can  cause  an improperly initialized memory structure to be
   freed.  In  most  cases, an intruder can use this flaw to crash PHP or
   the  web  server. Under some circumstances, an intruder may be able to
   take  advantage  of  this  flaw  to  execute  arbitrary  code with the
   privileges of the web server.

   You  may  be  aware that freeing memory at inappropriate times in some
   implementations  of  malloc  and  free  does not usually result in the
   execution  of  arbitrary  code.  However, because PHP utilizes its own
   memory  management  system,  the  implementation of malloc and free is
   irrelevant to this problem.

   Stefan  Esser  of  e-matters  GmbH has indicated that intruders cannot
   execute   code   on   x86   systems.   However,  we  encourage  system
   administrators  to  apply  patches  on  x86  systems  as well to guard
   against denial-of-service attacks and as-yet-unknown attack techniques
   that may permit the execution of code on x86 architectures.

   This  vulnerability  was discovered by e-matters GmbH and is described
   in  detail  in  their  advisory.  The  PHP  Group  has  also issued an
   advisory.  A list of vendors contacted by the CERT/CC and their status
   regarding this vulnerability is available in VU#929115.

   Although   this  vulnerability  only  affects  PHP  4.2.0  and  4.2.1,
   e-matters  GmbH  has  previously  identified  vulnerabilities in older
   versions  of  PHP.  If  you  are  running  older  versions  of PHP, we
   encourage you to review
   http://security.e-matters.de/advisories/012002.html

II. Impact

   A  remote  attacker can execute arbitrary code on a vulnerable system.
   An  attacker  may not be able to execute code on x86 architectures due
   to  the way the stack is structured. However, an attacker can leverage
   this  vulnerability  to  crash PHP and/or the web server running on an
   x86 architecture.

III. Solution

Apply a patch from your vendor

   Appendix A contains information provided by vendors for this advisory.
   As  vendors report new information to the CERT/CC, we will update this
   section  and note the changes in our revision history. If a particular
   vendor  is  not  listed  below,  we  have not received their comments.
   Please contact your vendor directly.

Upgrade to the latest version of PHP

   If  a  patch  is  not  available  from your vendor, upgrade to version
   4.2.2.

Deny POST requests

   Until  patches  or an update can be applied, you may wish to deny POST
   requests.  The  following  workaround  is  taken from the PHP Security
   Advisory:

     If  the  PHP  applications on an affected web server do not rely on
     HTTP POST input from user agents, it is often possible to deny POST
     requests on the web server.

     In  the  Apache  web server, for example, this is possible with the
     following  code  included  in  the  main  configuration  file  or a
     top-level .htaccess file:

     <Limit POST>
        Order deny,allow
        Deny from all
     </Limit>

     Note  that an existing configuration and/or .htaccess file may have
     parameters contradicting the example given above.

Disable vulnerable service

   Until  you  can upgrade or apply patches, you may wish to disable PHP.
   As a best practice, the CERT/CC recommends disabling all services that
   are not explicitly required. Before deciding to disable PHP, carefully
   consider your service requirements.

Appendix A. - Vendor Information

   This  appendix  contains  information  provided  by  vendors  for this
   advisory.  As  vendors  report new information to the CERT/CC, we will
   update this section and note the changes in our revision history. If a
   particular  vendor  is  not  listed  below, we have not received their
   comments.

Apple Computer Inc.

          Mac  OS  X  and  Mac  OS X Server are shipping with PHP version
          4.1.2  which  does  not  contain the vulnerability described in
          this alert.

Caldera

          Caldera  OpenLinux  does  not provide either vulnerable version
          (4.2.0,  4.2.1)  of  PHP  in their products. Therefore, Caldera
          products are not vulnerable to this issue.

Compaq Computer Corporation

          SOURCE:  Compaq Computer Corporation, a wholly-owned subsidiary
          of  Hewlett-Packard  Company  and  Hewlett-Packard  Company  HP
          Services Software Security Response Team
          x-ref: SSRT2300 php post requests
          At  the  time  of  writing  this  document, Compaq is currently
          investigating   the   potential  impact  to  Compaq's  released
          Operating System software products.
          As  further  information  becomes available Compaq will provide
          notice  of  the  availability  of any necessary patches through
          standard  security bulletin announcements and be available from
          your normal HP Services supportchannel.

Cray Inc.

          Cray, Inc. does not supply PHP on any of its systems.

Debian

          Debian GNU/Linux stable aka 3.0 is not vulnerable.
          Debian GNU/Linux testing is not vulnerable.
          Debian GNU/Linux unstable is vulnerable.
          The  problem  effects PHP versions 4.2.0 and 4.2.1. Woody ships
          an  older  version  of  PHP  (4.1.2),  that doesn't contain the
          vulnerable function.

FreeBSD

          FreeBSD  does not include any version of PHP by default, and so
          is  not  vulnerable; however, the FreeBSD Ports Collection does
          contain  the  PHP4  package. Updates to the PHP4 package are in
          progress  and a corrected package will be available in the near
          future.

Guardian Digital

          Guardian  Digital  has not shipped PHP 4.2.x in any versions of
          EnGarde, therefore we are not believed to be vulnerable at this
          time.

Hewlett-Packard Company

          SOURCE:  Hewlett-Packard Company Security Response Team
          At  the  time  of  writing  this  document,  Hewlett Packard is
          currently  investigating  the potential impact to HP's released
          Operating System software products.
          As further information becomes available HP will provide notice
          of  the  availability of any necessary patches through standard
          security  bulletin  announcements  and  be  available from your
          normal HP Services support channel.

IBM

          IBM  is  not vulnerable to the above vulnerabilities in PHP. We
          do  supply the PHP packages for AIX through the AIX Toolbox for
          Linux  Applications.  However,  these packages are at 4.0.6 and
          also incorporate the security patch from 2/27/2002.

Mandrakesoft

          Mandrake Linux does not ship with PHP version 4.2.x and as such
          is  not  vulnerable.  The  Mandrake Linux cooker does currently
          contain  PHP  4.2.1  and  will  be  updated shortly, but cooker
          should  not be used in a production environment and no advisory
          will be issued.

Microsoft Corporation

          Microsoft  products  are not affected by the issues detailed in
          this advisory.

Network Appliance

          No Netapp products are vulnerable to this.

Red Hat Inc.

          None  of  our commercial releases ship with vulnerable versions
          of PHP (4.2.0, 4.2.1).

SuSE Inc.

          SuSE Linux is not vulnerable to this problem, as we do not ship
          PHP 4.2.x.
     _________________________________________________________________

   The  CERT/CC acknowledges e-matters GmbH for discovering and reporting
   this vulnerability.
     _________________________________________________________________

   Author: Ian A. Finlay.
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2002-21.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: cert@cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
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          U.S.A.

   CERT/CC   personnel   answer  the  hotline  08:00-17:00  EST(GMT-5)  /
   EDT(GMT-4)  Monday  through  Friday;  they are on call for emergencies
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   NO WARRANTY
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   Engineering  Institute  is  furnished  on  an  "as is" basis. Carnegie
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   Copyright 2002 Carnegie Mellon University.

   Revision History
July 22, 2002:  Initial release




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