RE: Webwasher CSM Appliance Script Security Restriction Bypass

["Frank Berzau" <frank () cyberguard com>]

The Proactive Security Filter is one of several security filters in the
Webwasher CSM Suite. It can block or mitigate many day zero threats
before their signature is added to the integrated Antivirus engines.
While we never claimed it can detect 100% of new malware, we are
continously improving the filter and welcome every input about new
attack vectors.

To respond to your posting:

1) First tests today do not confirm that (at least the current version
of the product) is vulnerable as described. We checked the code and ran
a few tests and confirmed that the handling is case in-sensitive. We'll
run more tests and also check older versions after the Christmas
holidays.

2) What we need from you is a proof of concept script that you think
should be mitigated by the Proactive Filter but is not. Please contact
me directly so we can work together to further improve our Proactive
Security Filter.

Btw, we have double-checked our records and found no evidence of being
contacted prior to this posting yesterday. We have attempted to contact
you, but got no response (so far). Also, we believe the timing of this
posting - a day before Christmas - is very bad and not intented to
giving us a fair chance to resolve this as quickly as we normally could.

Thanks, Frank

-----------------------------------------------------
Frank Berzau
Director, European Support
CyberGuard Corp.
 

-----Original Message-----
From: d0t v0rt3x [mailto:d0tv0rt3x () gmail com] 
Sent: Thursday, December 22, 2005 9:42 PM
To: full-disclosure () lists grok org uk; bugtraq () securityfocus com
Subject: Webwasher CSM Appliance Script Security Restriction Bypass

Vendor: Webwasher (http://www.webwasher.com/)
Product: Webwasher CSM Appliance
Affected versions: CSM Suite 5.x
Author: .v0rt3x (d0tv0rt3x[at]gmail[d0t]com)
Date: 2005-Dec-22

....Background....
"...Webwasher appliances provide high-performance "Proactive
Filtering" of bidirectional SMTP, HTTP, HTTPS, and FTP traffic to
detect and cleanse all forms of malware. The result is a security
appliance that delivers the Blended Protection you need to protect
against malicious content and unwanted email..."

....Description....
Webwasher CSM includes an encapsulation script mechanism with the aim
of filtering malicious scripts.
The encapsulation script makes use of specific potentially malicious
tokens in order to detect and neutralize the malicious script.
The detection of the tokens is case sensitive. However, some of the
tokens can be executed whether they are written in lower case or upper
case letters.
In other words, by creating a specially crafted script, an attacker
can bypass the filtering mechanism and execute malicious scripts.

....Proof.of.Concept....
1) Create a malicious script by using an object which executes ".Run"
method (e.g. one of the many WScript.Shell exploits).
2) Replace ".Run" with ".run".
3) Execute the malicious script "safely" through Webwasher CSM.

....Timeline....
2005-May-15: Vendor was notified by mail.
2005-Aug-15: Vendor was notified again via contact form.
2005-Dec-22: No response from the vendor - public disclosure.