Software Engineering Institute

WebDAV is an extension to HTTP used to manage content on web servers. Quoting from RFC 2518:

[WebDAV is] an extension to the HTTP/1.1 protocol that allows clients to perform remote web content authoring operations. This extension provides a coherent set of methods, headers, request entity body formats, and response entity body formats that provide operations for:  Properties [...], Collections [... and], Namespace Operations.

A vulnerability in the Microsoft implementation of WebDAV can be used to disrupt IIS 5.0. Quoting from MS01-044,

A denial of service vulnerability [exists] that could enable an attacker to temporarily disrupt service on an IIS 5.0 web server. WebDAV doesn't correctly handle [a] particular type of very long, invalid request. Such a request would cause the IIS 5.0 service to fail; by default, it would automatically restart.

WebDAV is installed and operational by default on Microsoft IIS 5.0. This does not affect IIS 4.0 servers.

An intruder can cause the IIS 5.0 service to fail. It will restart by default.

Apply a patch as described in MS01-044. This is a cumulative patch that addresses a number of security problems discovered prior to August 15, 2001.