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Alkacon OpenCms 6.0.2 login Cross Site Scripting

scip AG Vulnerability Advisory ID 1910 (11/22/2005)
http://www.scip.ch/cgi-bin/smss/showadvf.pl?id=1910

I. INTRODUCTION

Alkacon OpenCms is a professional level open source website content
management system. OpenCms helps to create and manage complex websites
easily without knowledge of html.

More Information are available on the official Alkacon product web site
at the following URL:

    http://www.opencms.org

II. DESCRIPTION

Users are able to login to the system over the web front end by
accessing /system/login. In there the user name and the corresponding
password is required. If a wrong password is used, an error message will
occur. On this re-loaded web site the user name from the last login
attempt is re-written to the textbox ocUname.

An attacker may use the string "> to inject his own html or active code.
An important remark remains that the http request in this case is done
with the POST command which gives some limitations for the automated
remote-attack.

III. EXPLOITATION

To exploit this vulnerability no dedicated exploit is required. As
described before the classic script and code injection can be realized
with the string "> on the beginning of users input. A proof-of-concept
can be realised with the following input line:

   "><script>alert('scip');</script>

A plugin for our open-source exploiting framework "Attack Tool Kit"
(ATK) will be published in the near future. [1]

IV. IMPACT

This is a serious problem due the fact non-authenticated users are able
to launch such an attack.

The main limitation of the vulnerability remains in the fact that HTTP
POST requests are used. Thus, fully automated attacks are not easy to
launch.

V. DETECTION

Detection of web based attacks require a specialiced web proxy and/or
intrusion detection system. Patterns for such a detection are available
and easy to implement. Especially active code should not be part of user
inputs.

VI. WORKAROUND

The administrative web frontend of OpenCms should be protected by
further access limitations (e.g. htaccess authentication) and/or
firewalling.

VII. VENDOR RESPONSE

Alkacon has been informed on an early stage on 11/01/2005 via email to
info-at-alkacon.com. Within the first response the fix for the CVS HEAD
repository and a fixed release 6.0.3 was announced for the same month.
Everything was handled very professional and quickly by the vendor.

VIII. SOURCES

scip AG - Security Consulting Information Process (german)
http://www.scip.ch

scip AG Vulnerability Database (german)
http://www.scip.ch/cgi-bin/smss/showadvf.pl?id=1910

computec.ch document data base, web server documents (german)
http://www.computec.ch/download.php?list.26

IX. DISCLOSURE TIMELINE

10/27/05 Detection of the flaw
11/01/05 Reporting the flaw to Alkacon via email
11/09/05 First response by Alexander Kandzior, Alkacon Software
11/10/05 Immediate fix on the CVS HEAD repository
11/25/05 Official release of OpenCms 6.0.3 inclusive fixes
12/15/05 Public advisory by scip AG

IX. CREDITS

The vulnerability was discovered by Marc Ruef.

    Marc Ruef, scip AG, Zuerich, Switzerland
    maru-at-scip.ch
    http://www.scip.ch

A1. BIBLIOGRAPHY

[1] http://www.computec.ch/projekte/atk/

A2. LEGAL NOTICES

Copyright (c) 2005 scip AG, Switzerland.

Permission is granted for the re-distribution of this alert. It may not
be edited in any way without permission of scip AG.

The information in the advisory is believed to be accurate at the time
of publishing based on currently available information. There are no
warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect
or consequential loss or damage from use of or reliance on this
advisory.

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