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June 28, 2007: Pubcookie Login Server Security Advisory
Component:  Modules
Audience:  All
Modified:  June 28, 2007

June 28, 2007: Pubcookie login server security advisory.

Subject:       XSS Vulnerability in Pubcookie Login Server
Author:        Nathan Dors, Pubcookie Project
Status:        Confirmed, Patches Released
Threat Class:  Cross-Site Scripting
Issue date:    June 28, 2007
Severity:      Critical

Summary:
========

A new Pubcookie release and security patch file are available to address 
a Cross-Site Scripting (XSS) vulnerability found in the Pubcookie login
server.

We have no evidence that others have discovered the new vulnerability or
that it has been exploited anywhere "in the wild".

Sites running a Pubcookie login server are strongly advised to read this
security advisory and carry out the suggested actions below.

Note: The URL for this security advisory is:
http://pubcookie.org/news/20070606-login-secadv.html

Vulnerability Details:
======================

A new non-persistent XSS vulnerability was found in the Pubcookie login
server's compiled binary "index.cgi" CGI program. The CGI program
mishandles untrusted data when printing responses to the browser. This
makes the program 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
his or her local Pubcookie login page and attempt to exploit the XSS
vulnerability.

Threat Classification:
======================

This vulnerability is classified as *critical* due to the nature and
purpose of the Pubcookie login server for user authentication and Web
Single Sign-on (SSO). Specific threats include:

*) An attacker who injects malicious script by exploiting the
vulnerability might steal private Pubcookie data including a user's
authentication assertion ("granting") cookies and SSO ("login") session
cookies;

*) An attacker who injects HTML tags through the vulnerabilities might
deface a site's Pubcookie login page for a single visit by a single user
(i.e. a non-persistent defacement).

Note, however, that user authentication credentials (usernames and
passwords) are *not* vulnerable to maliciously injected script as they
were in the XSS vulnerabilities addressed and disclosed in May 2006. This
new vulnerability is limited to a specific stage in the message flow.

Affected Versions:
==================

This advisory applies to all versions of the Pubcookie login server's
"index.cgi" compiled binary CGI program.

Patch Releases:
===============

The following patch release addresses the reported XSS vulnerability:
* 3.3.2d (current production release)

This release is available now from the project's downloads page:
* http://pubcookie.org/downloads.html

A patch file is also available:
* http://pubcookie.org/downloads/pbc-login-server-security-fix-3_3_2c-3_3_2d.patch

Suggested Action:
=================

All sites running a Pubcookie login server are strongly advised to pursue
the following course of action:

(1) Sites still using a 3.0, 3.1, or 3.2 login server should consider
upgrading to the current 3.3.2d patch release, or apply the new login
server security patch file.

(2) Sites using a 3.3 login server should upgrade to the patched 3.3.2d
release.

(3) Sites using locally modified versions of the login server should apply
the new login server security patch file.

Note: For detailed version compatibility notes and upgrade information,
consult the relevant Pubcookie login server administration guide online.

Project Response:
=================

* 25 May 2007: Vulnerabilities discovered.
* 25 May 2007: Initial contact with technical details of vulnerability.
* 29 May 2007: Initial response confirming exploit and severity.
* 11 Jun 2007: Patch release/file available for vulnerability.
* 28 Jun 2007: Public disclosure thru pubcookie.org advisory.

Acknowledgments:
================

The Pubcookie project thanks Bradley Schwoerer of the University of
Wisconsin-Madison for reporting this security vulnerability.

References:
===========

Web Security Threat Classification
http://www.webappsec.org/projects/threat/


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Modified: June 28, 2007