Buffer overflow in Microsoft command processor (CMD.EXE) for Windows NT and Windows 2000 allows a local user to cause a denial of service via a long environment variable, aka the "Malformed Environment Variable" vulnerability.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-027
http://www.securityfocus.com/bid/1135
http://archives.neohapsis.com/archives/bugtraq/2000-04/0147.html