The w3svc.dll ISAPI filter in Front Page Server Extensions and ASP.NET for Internet Information Server (IIS) 4.0, 5.0, and 5.1 does not properly handle the error condition when a long URL is provided, which allows remote attackers to cause a denial of service (crash) when the URL parser accesses a null pointer.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2002/ms02-018
http://www.securityfocus.com/bid/4479
http://www.kb.cert.org/vuls/id/521059
http://www.iss.net/security_center/static/8800.php
http://www.cisco.com/warp/public/707/Microsoft-IIS-vulnerabilities-MS02-018.shtml