Windows Workstation Service - New unpatched vulnerability

There is also a POC exploit published for this new vulnerability. 

Windows Workstation Service - New unpatched vulnerability
http://www.frsirt.com/english/advisories/2006/5142

QUOTE: A vulnerability has been identified in Microsoft Windows, which could be exploited by attackers to cause a denial of service. This issue is due to an error in the Workstation Service that does not properly handle specially crafted "NetrWkstaUserEnum()" requests, which could be exploited by attackers to cause a vulnerable service to crash or exhaust all available memory resources, creating a denial of service condition.

Affected Products: Windows XP and 2000

Solution: Block ports 139 and 445 at the firewall.