• Article

Security Bulletin

Microsoft Security Bulletin MS99-029 - Important

Patch Available for "Malformed HTTP Request Header" Vulnerability

Published: August 11, 1999 | Updated: March 21, 2003

Version: 2.0

Patch Availability Information Updated: March 21, 2003

Originally Posted: August 11, 1999

Re-released: August 16, 1999

Summary

Microsoft has released a patch that eliminates a vulnerability in web server products that use Microsoft® Internet Information Server 4.0 as their web engine. The vulnerability could be used to mount denial of service attacks against the web server. This patch originally was released on August 11, 1999, but was found to contain a regression error. The regression error has been eliminated and the new patch is now available.

Frequently asked questions regarding this vulnerability can be found at https://www.microsoft.com/technet/security/bulletin/fq99-029.mspx

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

    Note   Although the vulnerability lies in IIS 4.0, several other Microsoft products also are affected because they use IIS 4.0 as their web engine. The patch can be applied to these products as well:

  • Microsoft Site Server 3.0

  • Microsoft Site Server 3.0, Commerce Edition

  • Microsoft Commerce Internet System 2.0 and 2.5

Vulnerability Identifier: CVE-1999-0867

Patch Availability

More Information

Please see the following references for more information related to this issue.

  • Microsoft Security Bulletin MS99-029: Frequently Asked Questions, https://www.microsoft.com/technet/security/bulletin/MS99-029faq.mspx.

  • Microsoft Knowledge Base (KB) article 238349, Specially-Malformed Header in HTTP Request Creates Denial of Service, </https:>https:.

    Note    It may take 24 hours from the original posting of this bulletin for the KB article to be visible.

  • Microsoft Security web site, </https:>https:.

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting Microsoft Technical Support is available at </https:>https:.

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.
  • August 16, 1999: Patch re-released
  • V2.0 (March 21, 2003): Introduced versioning and updated patch availability information

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