NetDDE Agent on Windows NT 4.0, 4.0 Terminal Server Edition, Windows 2000, and Windows XP allows local users to execute arbitrary code as LocalSystem via "shatter" style attack by sending a WM_COPYDATA message followed by a WM_TIMER message, as demonstrated by GetAd, aka "Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A681
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2002/ms02-071
http://www.securityfocus.com/bid/5927
http://www.packetstormsecurity.nl/filedesc/GetAd.c.html
http://www.iss.net/security_center/static/10343.php