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.