SEC-CONSULT Security Advisory 20051212-0

              title: Nortel SSL VPN Cross Site Scripting/Command
                     Execution
            program: Nortel SSL VPN
 vulnerable version: 4.2.1.6
           homepage: www.nortel.com
              found: 2005-05-30
                 by: Daniel Fabian / SEC-CONSULT / www.sec-consult.com

==========================================================================

Product Description:

The Nortel SSL VPN is a remote access security solution. By using secure
sockets layer (SSL) as the underlying security protocol, Nortel SSL VPN
allows for using the Internet for remote connectivity and the ubiquitous
Web browser as the primary client interface.

Vulnerabilty overview:

Due to insufficient input validation within the appliance's web interface,
it is possible for an attacker to supply his victim with a malicious link
that results in code execution on the victim's client. The problem has
been reproduced with version 4.2.1.6, however other versions might be
vulnerable as well.

Vulnerability details:

Due to insufficient input validation within the web interface of Nortel's
SSL VPN appliance, it is possible to hide commands in links to certain
pages of the web interface. As the Java Applet which is called from those
web pages is cryptographically signed, it may execute operating system
commands with the priviledges of the user sitting in front of the browser.

An attacker can thus supply his victim with a malicious link where
commands are hidden. If the victim clicks on the link and logs onto the
SSL VPN web interface (where it is automatically taken), arbitrary
commands are executed locally on the client of the victim.

Here is an example for a crafted link that executes the command "cmd.exe
/c echo test > c:\\test" (please consider the link one line):

—cut here—

https://SSL_VPN_SERVER/tunnelform.yaws?a=+cmd.exe+/c+echo+test+%3E+
c:\\test.txt+&type=Custom&sp=443&n=1&ph=&pp=&0tm=tcp&0lh=127.0.0.1&
0lp=8080&0hm=&0rh=10.10.10.10&0rp=80&sslEnabled=on&start=Start…

—cut here—

Vulnerable versions:

Nortel SSL VPN 4.2.1.6

Patch Status

According to vendor, a patch for this vulnerability has been incorporated
into maintainence release v5.1.5 of its VPN Gateway.

Vendor status:

vendor notified: 2005-05-30
vendor response: 2005-06-21
patch available: 2005-11-15
public disclos.: 2006-12-12

General remarks

We would like to apologize in advance for potential nonconformities and/or
known issues.

This advisory can also be found online at
http://www.sec-consult.com/247.html.

SEC Consult conducts periodical information security workshops on ISO
27001/BS 7799 in cooperation with BSI Management Systems. For more
information, please refer to http://www.sec-consult.com/236.html

–

SEC Consult Unternehmensberatung GmbH

Office Vienna
Blindengasse 3
A-1080 Wien
Austria

Tel.: +43 / 1 / 890 30 43 - 0
Fax.: +43 / 1 / 890 30 43 - 15
Mail: office at sec-consult dot com
www.sec-consult.com

EOF Daniel Fabian / @2005
d.fabian at sec-consult dot com