Updated: March 21, 2006
Subject: XSS Vulnerability in Pubcookie App Server Modules
Author: Nathan Dors, Pubcookie Project
Status: Confirmed, Patches Released
Threat Class: Cross-Site Scripting
Issue date: March 6, 2006
New releases of Pubcookie are available to address Cross-Site Scripting
(XSS) vulnerabilities found in the Pubcookie application server modules
for Apache and Microsoft IIS.
System administrators running a Pubcookie application server are
strongly advised to read this security advisory and carry out the
suggested actions below.
Note: The URL for this security advisory is:
XSS vulnerabilities typically involve three principals: a vulnerable Web
site, an attacker, and an end-user. The attacker exploits the
vulnerability in the Web site such that script written by the attacker
is run by the user within the security context of the Web site.
XSS vulnerabilities can be classified as persistent or non-persistent,
depending on whether or not the script or HTML injected by the attacker
persists on the vulnerable Web site.
A persistent XSS vulerability allows the attacker to leave script or
HTML on the vulnerable Web site where it has the potential of being run
by multiple users without further involvement by the attacker. Blogs and
message boards are example places where persistent XSS vulnerabilities
are often exploited.
A non-persistent XSS vulnerability, on the other hand, doesn't allow the
attacker to stage script or HTML on the vulnerable Web site. Instead, he
or she must stage it elsewhere and then orchestrate some other means of
initiating the attack, very often requiring the user's unintentional
cooperation. Email, chat messages, and web pages are example places
where script might be staged to help exploit a non-persistent XSS
vulnerability. The user might trigger the attack simply by opening a
tainted message or Web page, or by clicking inadvertently on a tainted
Pubcookie Application Server Details:
Non-persistent XSS vulnerabilities were found in the Pubcookie Apache
module (mod_pubcookie) and ISAPI filter. These components mishandle
untrusted data when printing responses to the browser. This makes them
vulnerable to carefully crafted requests containing script or HTML. If
an attacker can lure an unsuspecting user to visit carefully staged
content, the attacker can use it to redirect the user to a vulnerable
Pubcookie application server and attempt to exploit the XSS
These vulnerabilities are classified as *high* due to the nature and
purpose of Pubcookie application servers for user authentication and Web
Single Sign-on (SSO). An attacker who injects malicious script through
the vulnerabilities might steal private Pubcookie data including a
user's authentication assertion ("granting") cookies and application
Apache module (mod_pubcookie): This advisory applies to the following
versions of the Pubcookie Apache module (including beta and final
releases): 1.x, 3.0.0, 3.1.0, 3.1.1, 3.2.0, 3.2.1, 3.2.1a and 3.3.0.
ISAPI filter: This advisory applies to the following versions of the
Pubcookie ISAPI filter (including beta and final releases): 3.1.0,
3.1.1, 3.2.1, 3.2.1a and 3.3.0.
The following patch releases address all known XSS vulnerabilities:
* 3.3.0a (current production release; Unix and Windows)
* 3.2.1b (Unix-only patch release)
These releases are available now from the project's dowloads page:
Application servers running an affected version should upgrade to one of
the patch releases. Version 3.3.0a is the current production release.
Note: For detailed version compatibility notes and upgrade information,
consult the relevant Pubcookie application server documentation.
* 18 Dec 2005: Vulnerabilities discovered.
* 18 Dec 2005: Initial contact with technical details of vulnerability.
* 18 Dec 2005: Initial response confirming exploit and severity.
* 05 Jan 2006: Initial patches available for hardness testing.
* 06 Feb 2006: Solutions available for all known vulnerabilities.
* xx Mar 2006: Coordinated public release of security advisory.
The Pubcookie project wishes to thank Ben Maurer of Carnegie Mellon
University for reporting the original XSS vulnerability and for advising
during the fixes.
The Pubcookie project also wishes to thank the following sites for their
participation in the security response: University of Wisconsin-Madison,
Carnegie Mellon University, Stockholm University, University of
Virigina, University of Washington.
Web Security Threat Classification
CERT Advisory CA-2000-02 Malicious HTML Tags Embedded in Client Web
Phishing With Super Bait
XSS (Cross Site Scripting) Cheat Sheet
The vendor has not provided us with any further information regarding this vulnerability.