Background
==========
Struts is an open source framework for building web applications. The
core of the Struts framework is a flexible control layer based on
standard technologies such as Java Servlets, JavaBeans, resource
bundles, and the Extensible Markup Language (XML). Struts can be used
with different Java engines, such as WebLogic, TomCat, JRun, etc.

Scope
=====
After identifying in Struts an error message echoing the path back to
the user, Hacktics has conducted a research of identifying a cross site
scripting vulnerability in the implementation of this error on different
application servers.

The Finding
===========
When attempting to access a non existent Struts action URL (including
the Struts URL suffix, e.g. .do), the struts request handler generates
an error echoing the path of the requested action. The mechanism
generating this error does not perform sufficient input validation nor
perform HTML encoding of the output, thus exposing the system, in some
environments, to a Cross Site Scripting attack.

For detailed description and exploit please visit
http://www.hacktics.com/AdvStrutsNov05.html

Versions Tested
===============
Vulnerable
  Struts 1.2.7 Running on WebLogic 8.1 SP4
  Struts 1.2.7 Running on WebLogic 8.1 SP5
  Struts 1.2.7 Running on Resin Web Server
Non Vulnerable
  Struts Running on Apache Tomcat 5.5.9
  Struts Running on Apache Tomcat 5.5.12

Solution
========
The Apache Struts group has been notified of this vulnerability on
November 3rd, and has fixed the problem in the new Struts release
(1.2.8). Upgrading to the new version will eliminate the threat.
Alternatively, a work around is available on existing versions by
configuring the web server to display custom error messages rather than
the default ones.



-----------------------
Irene Abezgauz
Application Security Consultant
Hacktics Ltd.
Mobile: +972-54-6545405
Web: http://www.hacktics.com