Advisory 02/2005: Remote code execution in Serendipity

[Christopher Kunz]

Hardened PHP Project
www.hardened-php.net


-= Security Advisory =-


Advisory: Remote code execution in Serendipity
Release Date: 2005/06/29
Last Modified: 2005/06/29
Author: Christopher Kunz <christopher.kunz@hardened-php.net>
Application: Serendipity <= 0.8.2
Severity: Arbitrary remote code execution
Risk: Very High
Vendor Status: Vendor has released an updated version
References: http://www.hardened-php.net/advisory-022005.php


Overview:

Quote from http://www.s9y.org/:
"Serendipity is a weblog/blog system, implemented with PHP. It is standards
compliant, feature rich and open source (BSD License). Serendipity is
constantly under active development, with a team of talented developers
trying to make the best PHP powered blog on the net."


Details:

GulfTech Security [1] recently discovered a vulnerability in the PHP XML RPC
project [2] that leads to remote code execution. Unfortunately, this vulner-
ability also exists in the PEAR XMLRPC implementation, and GulfTech somewhat
neglected to notify the vendors in question.
Similar to the recently-discovered holes in PostNuke and Drupal, the
XML-RPC parser in Serendipity allows for remote code execution. An attacker
can send a forged POST request to the victim's blog and include PHP code in
the request body. This code is executed in the context of the affected
Serendipity instance.
Since the vulnerability is extremely easy to exploit and apart from one POST
request, no suspicious activity is logged, it could be used for automated
mass defacements and viral reproduction, similar to Santy.
The Hardened PHP project had knowledge of that kind of vulnerability for
some time now but tried to establish a responsible way of coordinating the
disclosure with all affected parties.
The maintainer of PEAR:ML_RPC has released an updated version that fixes
the vulnerability. The Serendipity team has released a fixed version, too.


CVE Information:

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2005-1921 to the vulnerability in PEAR:ML_RPC.


Proof of Concept:

The Hardened PHP Project is not going to release an exploit for
this vulnerability to the public.
It is trivial to implement, anyway.


Disclosure Timeline:

29. June 2005 - Vulnerability discovered and vendor notified
29. June 2005 - Vendor released bugfixed version
29. June 2005 - Public disclosure


Recommendation:

We urge you to update to the newest version of Serendipity, 0.8.2.
http://prdownloads.sourceforge.net/p...y-0.8.2.tar.gz
If, for some reason, that seems unfeasible, you should render the
file serendipity_xmlrpc.php unreadable by the web server to close the
most obvious attack vector.


References:

[ 1 ] http://www.gulftech.org/
[ 2 ] http://phpxmlrpc.sourceforge.net/


Copyright 2005 Christopher Kunz from the hardened PHP Project. All rights reserved.

[GulfTech Security Research]

"[2] that leads to remote code execution. Unfortunately, this vulner-
ability also exists in the PEAR XMLRPC implementation, and GulfTech
somewhat
neglected to notify the vendors in question."

This is a very unfair statement as I did my best to hunt down everyone
using the vulnerable libraries. Both the PEAR guys and the PHPXMLRPC
guys were contacted several days ago, and I also took the time to
personally contact everyone I could find using the vulnerable XMLRPC
libraries. I think it would be impossible for anyone to hunt down every
application using these libraries.

In regards to the vulnerabilities: No technical details will be released
by GulfTech until both libraries are updated because the holes are
identical and it would cause more harm than good. Anyone using either
vulnerable library should visit the official website pertaining to the
library and download any updated version. Again, technical details of
the vulnerabilities in these two libraries will be released in the future.

James

Christopher Kunz wrote:

> Hardened PHP Project
> www.hardened-php.net
>
>
> -= Security Advisory =-
>
>
> Advisory: Remote code execution in Serendipity
> Release Date: 2005/06/29
> Last Modified: 2005/06/29
> Author: Christopher Kunz <christopher.kunz@hardened-php.net>
> Application: Serendipity <= 0.8.2
> Severity: Arbitrary remote code execution
> Risk: Very High
> Vendor Status: Vendor has released an updated version
> References: http://www.hardened-php.net/advisory-022005.php
>
>
> Overview:
>
> Quote from http://www.s9y.org/:
> "Serendipity is a weblog/blog system, implemented with PHP. It is
> standards
> compliant, feature rich and open source (BSD License). Serendipity is
> constantly under active development, with a team of talented
> developers
> trying to make the best PHP powered blog on the net."
>
>
> Details:
>
>
>