Microsoft Security Bulletin (MS99-029)

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Microsoft Security Bulletin (MS99-029)
--------------------------------------

Patch Available for "Malformed HTTP Request Header" Vulnerability

Originally Posted: August 11, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability in web server
products that use Microsoft(r) Internet Information Server 4.0 as their web
engine. The vulnerability could be used to mount denial of service attacks
against the web server. Frequently asked questions regarding this
vulnerability can be found at
http://www.microsoft.com/security/bulletins/MS99-029faq.asp

Issue
=====
If multiple HTTP requests containing specially-malformed headers are sent to
an affected server, IIS may consume all memory on the server. If this
happens, IIS would be unable to service requests until either the clients
that issued the requests were closed, or the IIS service were stopped and
restarted. Once either of these actions have occurred, normal service would
be restored.

Affected Software Versions
==========================
 - Microsoft Internet Information Server 4.0
 - Microsoft Site Server 3.0
 - Microsoft Site Server 3.0, Commerce Edition
 - Microsoft Commerce Internet Server 2.0 and 2.5

Patch Availability
==================
 - X86 version:
   ftp://ftp.microsoft.com/bussys/iis/iis-public/fixes
   /usa/security/hdbrk-fix/x86
 - Alpha version:
   ftp://ftp.microsoft.com/bussys/iis/iis-public/fixes
   /usa/security/hdbrk-fix/alpha

   NOTE: Line breaks have been inserted in the above URLs for readability.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-029: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-029faq.asp.
 - Microsoft Knowledge Base (KB) article Q238349,
   Specially-Malformed Header in HTTP Request Creates Denial of Service,
   http://support.microsoft.com/support/kb/articles/q238/3/49.asp.
   (Note: It may take 24 hours from the original posting of this bulletin
   for the KB article to be visible.)
 - Microsoft Security Advisor web site,
   http://www.microsoft.com/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 acknowledges Nobuo Miwa of the LAC SNS team for bringing this
issue to our attention and working with us to alert customers about it.

Revisions
=========
 - August 11, 1999: Bulletin Created.

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(c) 1999 Microsoft Corporation. All rights reserved.

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