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TUCoPS :: Windows Net Apps :: ciacl081.txt

Microsoft Index Server Search Function Buffer Overflow





             __________________________________________________________

                       The U.S. Department of Energy
                     Computer Incident Advisory Center
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___
             __________________________________________________________

                             INFORMATION BULLETIN

             Microsoft Index Server Search Function Buffer Overflow
                     [Microsoft Security Bulletin MS01-025]

May 14, 2001 18:00 GMT                                            Number L-081
______________________________________________________________________________
PROBLEM:       An unchecked buffer exists in software processing search
               requests. This causes several potential vulnerabilities,
               depending on the format of an attacker's search request.
PLATFORM:      Indexing Service for Windows 2000, Index Server 2.0,
DAMAGE:        An attacker could run the code of choice within Local Security
               context, or cause denial of service to the Index server. Or, it
               could result in unauthorized file disclosure.
SOLUTION:      Apply the patch described below.
______________________________________________________________________________
VULNERABILITY  MEDIUM to HIGH, depending on network configuration. This
ASSESSMENT:    exploit requires access to Netbios across the network, so this
               is only exploitable if Netbios is allowed through firewalls. It is
               remotely exploitable.
______________________________________________________________________________

[****** Start Microsoft Advisory ******]

-----------------------------------------------------------------------
Title:      Index Server Search Function Contains Unchecked Buffer
Date:       10 May 2001
Software:   Index Server 2.0, Indexing Service for Windows 2000
Impact:     Run code of attacker's choice; file disclosure
Bulletin:   MS01-025

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS01-025.asp.
-----------------------------------------------------------------------

Issue:
======
The patches provided in the bulletin address two security
vulnerabilities that are unrelated to each other except in the sense
that both affect Index Server 2.0. The first vulnerability is a
buffer overrun vulnerability. Index Server 2.0 has an unchecked
buffer in a function that processes search requests. If an overly
long value were provided for a particular search parameter, it would
overrun the buffer. If the buffer were overrun with random data, it
would cause Index Server to fail. If it were overrun with carefully
selected data, code of the attacker's choice could be made to run on
the server, in the Local System security context. 

The second vulnerability affects both Index Server 2.0 and Indexing
Service in Windows 2000, and is a new variant of the "Malformed
Hit-Highlighting" vulnerability discussed in Microsoft Security
Bulletin MS00-006
(http://www.microsoft.com/technet/security/bulletin/MS00-006.asp).
The new variant has almost the same scope as the original
vulnerability, but potentially exposes a new file type If an attacker
provided an invalid search request, she could read "include" files
residing on the web server. The new patch eliminates all known
variants of the vulnerability. 

Mitigating Factors:
====================
Index Server 2.0 buffer overrun: 
 - The vulnerability only affects Index Server 2.0. Indexing 
   Services in Windows 2000 is not affected by it. 
 - In order to exploit the vulnerability, the attacker would 
   need the ability to authenticate to the server and to 
   create a named pipe connection to it (which requires access
   to NetBIOS, which should be blocked at the firewall). As a 
   result, it is likely that this vulnerability could, in a 
   properly configured network, only be exploited by an intranet 
   user. 
 - Index Server 2.0 is not provided as part of Windows NT 4.0; 
   instead, it is part of the Windows NT 4.0 Option Pack. It 
   installs by default as part of that package, but does not run 
   by default. 
New Variant of "Malformed Hit-Highlighting" vulnerability: 
 - The vulnerability would only allow files to be read. They 
   could not be added, changed or deleted via this vulnerability. 
 - Server-side "include" files should not contain sensitive data. 
   If this recommendation has been followed, there would be no 
   sensitive data to compromise via this vulnerability. 
 - The vulnerability would only allow files residing on the web 
   server - and in the same logical drive as the server's root 
   directory - to be read. It would not allow files elsewhere 
   on the server, or files residing on a remote server, to be read. 

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-025.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - David Litchfield of @Stake (http://www.atstake.com) for reporting
   the Index Server 2.0 buffer overrun.
 - Mike Mulling (http://www.gap.com) for reporting the new variant 
   of the "Malformed Hit-Highlighting" vulnerability 

----------------------------------------------------------------------

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
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OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.

[****** End Microsoft Advisory ******]
_______________________________________________________________________________

CIAC wishes to acknowledge the contributions of Microsoft for the
information contained in this bulletin.
_______________________________________________________________________________

CIAC, the Computer Incident Advisory Center, 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.

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can be contacted at:
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    E-mail:   ciac@ciac.org

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

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PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
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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
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recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
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Government or the University of California, and shall not be used for
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