l i n u x - u s e r s - g r o u p - o f - d a v i s
L U G O D
 
Next Meeting:
September 2: Social gathering
Next Installfest:
TBD
Latest News:
Aug. 18: Discounts to "Velocity" in NY; come to tonight's "Photography" talk
Page last updated:
2002 Jun 18 10:20

The following is an archive of a post made to our 'vox mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
[vox] Apache httpd: vulnerability with chunked encoding (fwd)
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[vox] Apache httpd: vulnerability with chunked encoding (fwd)



Just so you know... if you run an apache web server, you may want to watch
for the new version if the latest remote risk should impact you...

(Mostly for 64 bit systems and win32 based dists, but still limited DoS
for 32 bit linux systems.)

(Yet another reason for you to sign up to bugtraq)

I expect some discussion to take place about this, but this is the only
post on this that I will forward to these lists.

Enjoy,

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS/CM$/IT$/LS$/S/O$ !d--(++) !s !a+++(-----) C++$(++++) U++++$(+$) P+$>+++ 
L+++$(++) E W+++$(+) N+ o K w+$>++>+++ O-@ M+$ V-$>- !PS !PE Y+ !PGP
t@-(++) 5+@ X@ R- tv- b++ DI+++ D+ G--@ e+>++>++++ h(++)>+ r*>? z?
------END GEEK CODE BLOCK------
decode: http://www.ebb.org/ungeek/ about: http://www.geekcode.com/geek.html

---------- Forwarded message ----------
Date: Mon, 17 Jun 2002 18:21:15 +0100 (BST)
From: Mark J Cox <mjc@apache.org>
To: bugtraq@securityfocus.com
Subject: Apache httpd: vulnerability with chunked encoding

-----BEGIN PGP SIGNED MESSAGE-----


Date: June 17, 2002
Product: Apache Web Server
Versions: Apache 1.3 all versions including 1.3.24, Apache 2 all versions
up to 2.0.39

Introduction:

While testing for Oracle vulnerabilities, Mark Litchfield discovered a
denial of service attack for Apache on Windows.  Investigation by the
Apache Software Foundation showed that this issue has a wider scope, which
on some platforms results in a denial of service vulnerability, while on
some other platforms presents a potential a remote exploit vulnerability.  

We were also notified today by ISS that they had published the same issue
which has forced the early release of this advisory.

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2002-0392 to this issue.

Description:

Versions of the Apache web server up to and including 1.3.24 and 2.0 up to
and including 2.0.36 and 2.0.36-dev versions contain a bug in the routines
which deal with invalid requests which are encoded using chunked encoding.
This bug can be triggered remotely by sending a carefully crafted invalid
request. This functionality is enabled by default.

In most cases the outcome of the invalid request is that the child process
dealing with the request will terminate.  At the least, this could help a
remote attacker launch a denial of service attack as the parent process
will eventually have to replace the terminated child process and starting
new children uses non-trivial amounts of resources.

On the Windows and Netware platforms, Apache runs one multithreaded child
process to service requests.  The teardown and subsequent setup time to
replace the lost child process presents a significant interruption of
service.  As the Windows and Netware ports create a new process and reread
the configuration, rather than fork a child process, this delay is much
more pronounced than on other platforms.

In Apache 2.0 the error condition is correctly detected, so it will not
allow an attacker to execure arbitrary code on the server. However
platforms could be using a multithreaded model of multiple concurrent
requests per child process (although the default preference remains
multiple processes with a single thread and request per process, and most
multithreaded models continue to create multiple child processes).  Using
any multithreaded model, all concurrent requests currently served by the
affected child process will be lost.

In Apache 1.3 the issue causes a stack overflow.  Due to the nature of the
overflow on 32-bit Unix platforms this will cause a segmentation violation
and the child will terminate.  However on 64-bit platforms the overflow
can be controlled and so for platforms that store return addresses on the
stack it is likely that it is further exploitable. This could allow
arbitrary code to be run on the server as the user the Apache children are
set to run as.

We have been made aware that Apache 1.3 on Windows is exploitable in this
way.

Please note that the patch provided by ISS does not correct this
vulnerability.

The Apache Software Foundation are currently working on new releases that
fix this issue, please see http://httpd.apache.org/ for updated
versions.










-----BEGIN PGP SIGNATURE-----
Version: PGP 6.5.8

iQCVAwUBPQ4aj+6tTP1JpWPZAQHIDwP/UrFoCphthG1gd82ZaAQT0hjCaExlFaM2
p8BY5P6JS7VrRlzUoGd/7GRBF9o7foNpgFlANx1NNttr8FhHqlRbFBZH6u1FmTpY
4zGq7GKFuZiiAKWaCaCFcpIQguJ1vlrJc49E9k9jvJhuyzh/0Jz/Lj/wAFgmctqm
6Q7MwIcb1bk=
=fZnx
-----END PGP SIGNATURE-----



_______________________________________________
vox mailing list
vox@lists.lugod.org
http://lists.lugod.org/mailman/listinfo/vox



LinkedIn
LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
facebook
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
Appahost Applications
For a significant contribution towards our projector, and a generous donation to allow us to continue meeting at the Davis Library.