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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
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
Pittsburgh PA 15213-3890
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
during other hours, on U.S. holidays, and on weekends.
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______________________________________________________________________
NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed or
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_________________________________________________________________
Conditions for use, disclaimers, and sponsorship information
Copyright 2002 Carnegie Mellon University.
Revision History
June 17, 2002: Initial release
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