Microsoft Internet Information Server 5.0 Patch: Malformed Extension Data in URL

From Microsoft:

This update resolves the "Malformed Extension Data in URL" security vulnerability in Internet Information Server (IIS) 5.0 and IIS 4.0. Installing this update will prevent a malicious user from slowing or temporarily stopping performance on your Web server. If the URL used by a malicious user to request a file on your Web server contained malformed file extension data, the server could become unresponsive. The vulnerability does not cause the server to fail, nor does it allow a malicious user to compromise data on the computer or to take administrative control over it.