Security Bulletin (MS00-030)

2000-05-12T00:00:00
ID SECURITYVULNS:DOC:181
Type securityvulns
Reporter Securityvulns
Modified 2000-05-12T00:00:00

Description

Microsoft Security Bulletin (MS00-030)


Patch Available for "Malformed Extension Data in URL" Vulnerability

Originally Posted: May 11, 2000

Summary

Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Internet Information Server. The vulnerability could be used to slow the performance of an affected server, or temporarily stop it altogether.

Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-030.asp

Issue

In compliance with RFC 2396, the algorithm in IIS that processes URLs has flexibility built in to allow it to process any arbitrary sequence of file extensions or subresource identifiers (referred to in the RFC as path_segments). By providing an URL that contains specially-malformed file extension information, a malicious user could misuse this flexibility in order to arbitrarily increase the work factor associated with parsing the URL. This could consume much or all of the CPU availability on the server and prevent useful work from being done.

The vulnerability does not provide any capability to cause the server to fail, or to add, change or delete data on it. Likewise, it provides no capability to usurp administrative control of the web server. The slowdown would only last until the URL had been processed, at which point service would return to normal.

Affected Software Versions

  • Microsoft Internet Information Server 4.0
  • Microsoft Internet Information Server 5.0

Patch Availability

  • Internet Information Server 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20906
  • Internet Information Server 5.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20904

Note: Additional security patches are available at the Microsoft Download Center

More Information

Please see the following references for more information related to this issue. - Frequently Asked Questions: Microsoft Security Bulletin MS00-030, http://www.microsoft.com/technet/security/bulletin/fq00-030.asp - Microsoft Knowledge Base article Q260205 discusses this issue and will be available soon. - RFC 2396, Uniform Resource Identifiers (URI): Generic Syntax, http://www.ietf.org/rfc/rfc2396.txt. - Microsoft TechNet Security web site, http://www.microsoft.com/technet/security/default.asp

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/support/contact/default.asp.

Acknowledgments

Microsoft thanks Underground Security Systems Research (http://www.ussrback.com) for reporting this vulnerability to us and working with us to protect customers.

Revisions

  • May 11, 2000: Bulletin Created.

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last updated May 11, 2000

(c) 2000 Microsoft Corporation. All rights reserved. Terms of use.