Overview

Cerberus FTP Server (http://www.cerberusftp.com/) is a secure and
reliable FTP server with many features and available functionality.

It was discovered that the Web Administration interface has multiple
persistent Cross Site Scripting (XSS) vulnerabilities. In the log
viewer there is a XSS vulnerability which may be used by an
unauthenticated user against an authenticated user. In the server
manager a trivial XSS vulnerability exists which may be used by the
authenticated user.

Analysis

To start, the vulnerabilities in the on the "/servermanger" page is
trivial to exploit by escaping the "<textarea>" tags for each
available server message.

The "/log" is less trivial to exploit in that the log page uses
async-javascript callbacks to collect and display log data to the
user. The log clears itself in 2-3 seconds as well. This occurs
normally on an 8 second cycle and I in my experience it was difficult
to have the log populated with appropriate attack vectors during a
window to achieve exploitation.

I believe an administrative user would have to be logged in at the
time of the attack and actively viewing the "/log" page to achieve
successful exploitation. Due to these limitations I believe this to
have a significant effect on the impact and reliability on any
possible exploit code.

For more discussion on these bugs I've created a brief write-up at:
http://sadgeeksinsnow.blogspot.com/2012/12/persistence-is-key-another-bug-hunt.html

Timeline

12/05/2012 - Discovered multiple bugs in product vendor's application
12/06/2012 - Disclosure of details to product vendor
12/07/2012 - Vendor created fixes for reported bugs
12/13/2012 - CVE Assignment
12/19/2012 - Public disclosure to Bugtraq

CVE(s)

CVE-2012-6339: Multiple XSS vulnerabilities in Cerberus FTP Web
Administration interface. Affected pages are "/log" and
"/servermanager".

Remediation

Update to the latest version of Cerberus FTP Server.

Special Thanks

Special Thanks to Grant @ Cerberus for his incredible response time
and dedication to secure coding principles.

For more information concerning myself or my research:
sadgeeksinsnow.blogspot.com