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__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Center
___ __ __ _ ___
/ | /_\ /
\___ __|__ / \ \___
__________________________________________________________
INFORMATION BULLETIN
Microsoft ISA Web Proxy Service Denial of Service
[Microsoft Bulletin MS01-021]
April 20, 2001 00:00 GMT Number L-073
______________________________________________________________________________
PROBLEM: The ISA server web proxy service does not correctly handle web
requests that contain a particular type of malformed argument.
Processing such a request would cause the web proxy service to
fail, blocking all incoming and outgoing requests until the
service is restarted.
PLATFORM: Microsoft ISA Server 2000
DAMAGE: Crashing the web proxy service would block all incoming and
outgoing requests creating a denial of service condition.
SOLUTION: Apply the patch as shown in Microsoft Security Bulletin
MS01-021.
http://www.microsoft.com/technet/security/bulletin/MS01-021.asp.
______________________________________________________________________________
VULNERABILITY The risk is LOW. Restarting the web proxy service clears the
ASSESSMENT: blockage. The vulnerability cannot allow an intruder to breach
security. The blockage does not disrupt any other services on
the ISA server.
______________________________________________________________________________
[***** Start Microsoft Security Bulletin *****]
- - -----------------------------------------------------------------------
Title: Invalid Web Request Can Cause Access Violation in ISA
Server Web Proxy Service
Date: 16 April 2001
Software: ISA Server 2000
Impact: Denial of service
Bulletin: MS01-021
Microsoft encourages customers to review the Security Bulletin
at: http://www.microsoft.com/technet/security/bulletin/MS01-021.asp.
- - -----------------------------------------------------------------------
Issue:
======
The ISA Server Web Proxy service does not correctly handle web
requests that contain a particular type of malformed argument.
Processing such a request would result in an access violation,
which would cause the Web Proxy service to fail. This would disrupt
all ingoing and outgoing web proxy requests until the service was
restarted.
Mitigating Factors:
====================
- The vulnerability could be exploited from the Internet only
if the Web Publishing feature were enabled. By default,
this feature is disabled.
- The vulnerability would not enable an attacker to breach the
security of the firewall - that is, it would not enable the
attacker to access protected resources or bypass the firewall.
It would only enable the attacker to deny legitimate service
to other users.
- The vulnerability would only allow the Web Proxy service to
be disrupted. Other ISA services would continue functioning
normally.
Patch Availability:
===================
- A patch is available to fix this vulnerability. Please read
Security Bulletin
http://www.microsoft.com/technet/security/bulletin/ms01-021.asp
for information on obtaining this patch.
Acknowledgment:
===============
- Dr. Richard Reiner, Graham Wiseman, Matthew Siemens, and
Kent Nicolson of FSC Internet Corp. / SecureXpert Labs
(http://www.fscinternet.com / http://www.securexpert.com)
- - ----------------------------------------------------------------------
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.
[***** End Microsoft Security Bulletin *****]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of Microsoft for the
information contained in this bulletin.
______________________________________________________________________________
CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.
CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
Voice: +1 925-422-8193 (7x24)
FAX: +1 925-423-8002
STU-III: +1 925-423-2604
E-mail: ciac@ciac.org
Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.
World Wide Web: http://www.ciac.org/
(or http://ciac.llnl.gov -- they're the same machine)
Anonymous FTP: ftp.ciac.org
(or ciac.llnl.gov -- they're the same machine)
PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins. If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.
This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.
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