Microsoft IIS web servers include ISAPI extensions which are invoked in the server process to handle requests of a given type.
A heap overflow in IIS 4.0 and 5.0 when processing chunked encoding transfers of HTR requests allows command execution.
Apply the patch referenced in Microsoft Security Bulletin 02-028.
Since this is a heap overflow vulnerability, the exploit only works in certain system states.
Windows 2000 / Windows 2000 SP1
Windows 2000 SP2