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AUSCERT External Security Bulletin Redistribution
ESB-1999.081 -- CERT Advisory CA-99-07
New Information regarding IIS Buffer Overflow
21 June 1999
The CERT Coordination Centre has released the following advisory containing
new information regarding the IIS buffer overflow vulnerability. New
information released by Microsoft has indicated that the vulnerability
affects several libraries, including libraries that handle .HTR, .STM,
and .IDC files. This vulnerability may allow remote intruders to crash
IIS and execute arbitrary code on the server with the privileges of IIS.
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CERT Advisory CA-99-07 IIS Buffer Overflow
Revised: June 18, 1999
Originally released: June 16, 1999
Note: This re-distribution of CA-99-07 contains new information
regarding variations of the IIS vulnerability that was widely reported
this week. In particular, we encourage sites to obtain and install the
patch that is available from Microsoft which addresses all of the
variations of this vulnerability.
* Machines running Microsoft Internet Information Server 4.0
Buffer overflow vulnerabilities affecting Microsoft Internet
Information Server 4.0 have been discovered in several libraries,
including libraries that handle .HTR, .STM, and .IDC files.
A tool to exploit at least one of the vulnerabilities has been
These vulnerabilities allow remote intruders to execute arbitrary code
with the privileges of the IIS server. Additionally, intruders can use
this vulnerability to crash vulnerable IIS processes.
Microsoft has released and updated Microsoft Security Bulletin
MS99-019, which points to a patch for these vulnerabilities. We
encourage you to read this bulletin, available from
We will update this advisory as more information becomes available.
Please check the CERT/CC Web site for the most current revision.
Our thanks to Jason Garms and Scott Culp of Microsoft for providing
information contained in this advisory.
This document is available from:
CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4)
Monday through Friday; they are on call for emergencies during other
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We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from http://www.cert.org/CERT_PGP.key.
If you prefer to use DES, please call the CERT hotline for more
Getting security information
CERT publications and other security information are available from
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Copyright 1999 Carnegie Mellon University.
Conditions for use, disclaimers, and sponsorship information can be
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Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed or
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fitness for a particular purpose or merchantability, exclusivity or
results obtained from use of the material. Carnegie Mellon University
does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
June 16, 1999: Initial release
June 18, 1999: Added information about .STM and .IDC files.
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This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to use any or all of this information is
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NOTE: This is only the original release of the security bulletin. It will
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Contact information for the authors of the original document is included
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