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.
* 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.
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
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.
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 comments.
Apache Software Foundation
New versions of the Apache software are available from:
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. does not distribute Apache with any of its operating systems.
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 products.
Microsoft does not ship the Apache web server.
NetApp systems are not vulnerable to this problem.
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.
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
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Copyright 2002 Carnegie Mellon University.
Revision History June 17, 2002: Initial release