SecurityvulnsSECURITYVULNS:DOC:181Security Bulletin (MS00-030)
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.
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Last updated May 11, 2000
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