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CERT Advisory CA-2002-17 Apache Web Server Chunk Handling Vulnerability

   Original release date: June 17, 2002
   Last revised: --
   Source: CERT/CC

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

Systems Affected

     * Web servers based on Apache code versions 1.3 through 1.3.24
     * Web servers based on Apache code versions 2.0 through 2.0.36

Overview

   There is a remotely exploitable vulnerability in the handling of large
   chunks  of  data  in web servers that are based on Apache source code.
   This  vulnerability  is present by default in configurations of Apache
   web  servers  versions  1.3  through  1.3.24  and versions 2.0 through
   2.0.36.  The  impact  of  this  vulnerability  is  dependent  upon the
   software version and the hardware platform the server is running on.

I. Description

   Apache is a popular web server that includes support for chunk-encoded
   data according to the HTTP 1.1 standard as described in RFC2616. There
   is  a  vulnerability  in  the  handling  of certain chunk-encoded HTTP
   requests that may allow remote attackers to execute arbitrary code.

   The  Apache  Software  Foundation has published an advisory describing
   the details of this vulnerability. This advisory is available on their
   web site at

          http://httpd.apache.org/info/security_bulletin_20020617.txt

II. Impact

   For  Apache  versions 1.3 through 1.3.24 inclusive, this vulnerability
   may allow the execution of arbitrary code by remote attackers. Several
   sources have reported that this vulnerability can be used by intruders
   to  execute  arbitrary  code  on  Windows platforms. Additionally, the
   Apache  Software  Foundation  has  reported  that a similar attack may
   allow the execution of arbitrary code on 64-bit UNIX systems.

   For  Apache  versions  2.0  through  2.0.36  inclusive,  the condition
   causing  the  vulnerability is correctly detected and causes the child
   process  to  exit.  Depending  on  a variety of factors, including the
   threading model supported by the vulnerable system, this may lead to a
   denial-of-service attack against the Apache web server.

III. Solution

Apply a patch from your vendor

   Apply  a  patch  from  your  vendor to correct this vulnerability. The
   CERT/CC  has  been informed by the Apache Software Foundation that the
   patch  provided  in the ISS advisory on this topic does not completely
   correct  this  vulnerability.  More  information about vendor-specific
   patches  can  be found in the vendor section of this document. Because
   the   publication  of  this  advisory  was  unexpectedly  accelerated,
   statements  from  all  of  the  affected vendors were not available at
   publication  time.  As  additional  information  from  vendors becomes
   available, this document will be updated.

Upgrade to the latest version

   The Apache Software Foundation has released two new versions of Apache
   that correct this vulnerability. System administrators can prevent the
   vulnerability  from  being  exploited  by  upgrading to Apache version
   1.3.25  or  2.0.39.  The new versions of Apache will be available from
   their web site at

          http://httpd.apache.org/

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.

Apache Software Foundation

   New versions of the Apache software are available from:

          http://httpd.apache.org/

Conectiva Linux

   The  Apache  webserver  shipped  with Conectiva Linux is vulnerable to
   this  problem.  New  packages fixing this problem will be announced to
   our mailing list after an official fix becomes available.

Cray, Inc.

   Cray,  Inc.  does  not  distribute  Apache  with  any of its operating
   systems.

IBM Corporation

   IBM  makes  the Apache Server availble for AIX customers as a software
   package  under  the  AIX-Linux  Affinity  initiative.  This package is
   included  on  the  AIX  Toolbox  for Linux Applications CD, and can be
   downloaded via the IBM Linux Affinity website. The currently available
   version of Apache Server is susceptible to the vulnerability described
   here.  We  will  update  our Apache Server offering shortly to version
   1.3.23,  including  the patch for this vulnerability; this update will
   be made available for downloading by accessing this URL:

          http://www-1.ibm.com/servers/aix/products/aixos/linux/download.
          html

   and following the instructions presented there.

   Please  note  that  Apache Server, and all Linux Affinity software, is
   offered on an "as-is" basis. IBM does not own the source code for this
   software,  nor  has  it developed and fully tested this code. IBM does
   not support these software packages.

Lotus

   We have verified that the Lotus Domino web server is not vulnerable to
   this  type of problem. Also, we do not ship Apache code with any Lotus
   products.

Microsoft Corporation

   Microsoft does not ship the Apache web server.

Network Appliance

   NetApp systems are not vulnerable to this problem.

RedHat Inc.

   Red  Hat  distributes  Apache  1.3  versions  in  all  Red  Hat  Linux
   distributions, and as part of Stronghold. However we do not distribute
   Apache  for Windows. We are currently investigating the issue and will
   work on producing errata packages when an official fix for the problem
   is  made  available.  When  these  updates  are  complete they will be
   available  from  the  URL below. At the same time users of the Red Hat
   Network will be able to update their systems using the 'up2date' tool.

          http://rhn.redhat.com/errata/RHSA-2002-103.html

Unisphere Networks

   The  Unisphere  Networks  SDX-300 Service Deployment System (aka. SSC)
   uses  Apache  1.3.24. We are releasing Version 3.0 using Apache 1.3.25
   soon, and will be issuing a patch release for SSC Version 2.0.3 in the
   very near future.
     _________________________________________________________________

   The CERT/CC thanks Mark Litchfield for reporting this vulnerability to
   the  Apache  Software  Foundation,  and  Mark  Cox  for reporting this
   vulnerability to the CERT/CC.
     _________________________________________________________________

   Author: Cory F. Cohen
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2002-17.html
   ______________________________________________________________________

CERT/CC Contact Information

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   Copyright 2002 Carnegie Mellon University.

   Revision History
June 17, 2002:  Initial release

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