Discovered by: Noam Rathaus using the beSTORM fuzzer.
Reported to vendor: December, 2005.
Vendor response: Microsoft does not consider this issue to be a security 
vulnerability.

Public release date: 4th of May, 2006.
Advisory URL: 
http://www.beyondsecurity.com/besirt/advisories/042006-001-ISA-LM.txt 

Introduction
------------
There is a Log Manipulation vulnerability in Microsoft ISA Server 2004, which 
when exploited will enable a malicious user to manipulate the Destination 
Host parameter of the log file.

Technical Details
-----------------
By sending the following request to the server:
GET / HTTP/1.0
Host: %01%02%03%04
Transfer-Encoding: whatever

We were able to insert arbitrary characters, in this case the ASCII characters
1, 2, 3 (respectively) into the Destination Host parameter of the log file.

This has been found after 3 days of running the beSTORM fuzzer at 600+ 
Sessions per Second while monitoring the ISA Server log file for problems.

About ISA Server 2004
---------------------
"Microsoft Internet Security and Acceleration (ISA) Server 2004 is the 
advanced stateful packet and application-layer inspection firewall, virtual 
private network (VPN), and Web cache solution that enables enterprise 
customers to easily maximize existing information technology (IT) investments 
by improving network security and performance."

Product URL: http://www.microsoft.com/isaserver/default.mspx 

--
beSIRT - Beyond Security's Incident Response Team
beSIRT@beyondsecurity.com. 

www.BeyondSecurity.com