Netscreen SSH1 CRC32 Compensation Denial of service

[Erik Parker <erik.parker () digitaldefense net>]

Discovered by: HD Moore
Products Tested: Netscreen-25 (All models expected to be vulnerable)
Vendor contacted: October 23rd
Vendor confirmed: October 23rd
CVE: CVE-2001-0144 covered this bug.

Original Bug discovered by: Michal Zalewski of the BindView RAZOR Team.

In February of 2001, BindView's RAZOR Team announced the SSH1 CRC32 
compensation attack detector bug. After all was said and done, several 
vendors found their SSH implementations were vulnerable.  Netscreen seems 
to have overlooked this for a year and 8 months.

By default the Netscreen does not ship with SSH enabled, and Netscreen 
usually doesn't encourage their customers to even access the CLI on their 
devices. However, in the GUI you can enabled SSH, and disable telnet. This 
only opens SSH on the trusted interfaces, unless you specifically add 
rules to forward to this interface/port. On a normal system with SSH 
enabled, the unit will only be vulnerable to attackers on the trusted side.

If you use any of the CRC32 exploits out there, the unit will crash 
immediately, and require a hard reboot. It does not appear from our 
analysis that anything more than a crash can occur from this. 

The vendor assured a response with an ETA to a fix by October 25th. After 
trying to get more information from them a few times after October 25th 
passed, it has fallen on deaf ears. 


--        
Erik Parker
Digital Defense, Inc.