Apache mod_security: Rule bypass

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200705-17 / mod_security
Release Date	May 17, 2007
Latest Revision	December 30, 2007: 02
Impact	low
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
www-apache/mod_security	< 2.1.1	>= 2.1.1	All supported architectures

Related bugreports: #169778

Synopsis

A vulnerability has been discovered in mod_security, allowing a remote attacker to bypass rules.

2. Impact Information

Background

mod_security is an Apache module designed for enhancing the security of the Apache web server.

Description

Stefan Esser discovered that mod_security processes NULL characters as terminators in POST requests using the application/x-www-form-urlencoded encoding type, while other parsers used in web applications do not.

Impact

A remote attacker could send a specially crafted POST request, possibly bypassing the module ruleset and leading to the execution of arbitrary code in the scope of the web server with the rights of the user running the web server.

3. Resolution Information

Workaround

There is no known workaround at this time.

Resolution

All mod_security users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=www-apache/mod_security-2.1.1"

4. References

CVE-2007-1359

Page updated May 17, 2007

Summary: This is a Gentoo Linux Security Advisory

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