The Workstation service in Microsoft Windows 2000 SP4 and XP SP2 allows remote attackers to cause a denial of service (memory consumption) via a large maxlen value in an NetrWkstaUserEnum RPC request.
https://www.exploit-db.com/exploits/3013
http://www.vupen.com/english/advisories/2006/5142
http://www.eeye.com/Resources/Security-Center/Research/Zero-Day-Tracker/2005/20051116