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

From: CERT Advisory (cert-advisory@cert.org)
Date: 06/18/02

Date: Mon, 17 Jun 2002 22:01:34 -0400 (EDT)
From: CERT Advisory <cert-advisory@cert.org>
To: cert-advisory@cert.org


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


   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


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


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

Apache Software Foundation

   New versions of the Apache software are available from:


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

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:


   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.


   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

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.


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:

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   Revision History
June 17, 2002: Initial release

Version: PGP 6.5.8


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