NGSSoftware Insight Security Research Advisory Name: IIS 5 & 5.1 Denial Of Service Vulnerability Systems Affected: Windows 2000 and XP all service packs. Severity: Moderate Category: Denial of Service Vendor URL: http://www.mircosoft.com Author: Mark Litchfield (markat_private) Date: 31st October 2002 Advisory number: #NISR31102002 Description *********** Microsofts Internet Information Server and Intranet Server 5.0 and 5.1 comes with a feature called WebDAV. WebDAV, or Web-based Distributed Authoring and Versioning, is the emerging standard in web-based collaboration. Simply put, WebDAV allows web development teams and other workgroups to use a remote web server as easily as if it were a local file server. Technically, WebDAV is a set of extensions to the HTTP protocol. Details ******* In this particular instance, a denial of service vulnerability exists due to a flaw in the way IIS 5.0 and 5.1 allocates memory for WebDAV requests. If a malformed WebDAV request was sent to the server, IIS would allocate an extremely large amount of memory on the server. By sending several such requests, an attacker could cause the server to fail. This vulnerability could only be exploited if the server allowed WebDAV requests to be levied on it and is also dependent upon the Indexing server service to be running. Whilst by default the relevant WebDAV request method is allowed, the Indexing Service is turned off by default. Fix Information *************** NGSSoftware alerted Microsoft to these problems on the 16th May 2002. A patch can be found at http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/ bulletin/MS02-062.asp Common Vulnerabilities & Exposures http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1182 A check for these issues has been added to Typhon II, of which more information is available from the NGSSoftware website: http://www.ngssoftware.com
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