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AUSCERT External Security Bulletin Redistribution
ESB-2001.202 -- Microsoft Security Bulletin MS01-025
Index Server Search Function Contains Unchecked Buffer
15 May 2001
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AusCERT Security Bulletin Summary
---------------------------------
Product: Index Server 2.0
Indexing Service for Windows 2000
Vendor: Microsoft
Operating System: Windows NT
Windows 2000
Impact: Execute Arbitrary Code/Commands
Read-only Data Access
Access Required: Local
Remote
Ref: ESB-2000.063
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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.
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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
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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.
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