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TUCoPS :: Windows Net Apps :: ciacl098.txt

Microsoft Index Server ISAPI Extension Buffer Overflow





             __________________________________________________________

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

                             INFORMATION BULLETIN

             Microsoft Index Server ISAPI Extension Buffer Overflow
                     [Microsoft Security Bulletin MS01-033]

June 19, 2001 17:00 GMT                                           Number L-098
______________________________________________________________________________
PROBLEM:       The idq.dll extension contains a buffer overflow in the code
               handling input URLs.
PLATFORM:      Windows NT, 2000; affects IIS web servers: Index Server 2.0 and
               Indexing Service.
DAMAGE:        The idq.dll executes in the system context, therefore this exploit
               could result in a system compromise, allowing the attacker
               to execute code of his/her choice.
SOLUTION:      Apply the patches described in Microsoft's bulletin
               immediately.
______________________________________________________________________________
VULNERABILITY  VERY HIGH. This vulnerability is remotely exploitable, and can
ASSESSMENT:    result in total system or Administrator compromise.
______________________________________________________________________________

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

- ----------------------------------------------------------------------
Title:      Unchecked Buffer in Index Server ISAPI Extension Could
            Enable Web Server Compromise
Date:       18 June 2001
Software:   Index Server 2.0 and Indexing Service
Impact:     Run code of attacker's choice
Bulletin:   MS01-033

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS01-033.asp.
- ----------------------------------------------------------------------

Issue:
======
As part of its installation process, IIS installs several ISAPI extensions -- .dlls that provide extended functionality. Among these is idq.dll, which is a component of Index Server (known in Windows 2000 as Indexing Service) and provides support for administrative scripts
(.ida files) and Internet Data Queries (.idq files). 

A security vulnerability results because idq.dll contains an unchecked buffer in a section of code that handles input URLs. An attacker who could establish a web session with a server on which idq.dll is installed could conduct a buffer overrun attack and execute code on the web server. Idq.dll runs in the System context, so exploiting the vulnerability would give the attacker complete control of the server and allow him to take any desired action on it. 

The buffer overrun occurs before any indexing functionality is requested. As a result, even though idq.dll is a component of Index Server/Indexing Service, the service would not need to be running in order for an attacker to exploit the vulnerability. As long as the script mapping for .idq or .ida files were present, and the attacker were able to establish a web session, he could exploit the vulnerability. 

Clearly, this is a serious vulnerability, and Microsoft urges all customers to take action immediately. Customers who cannot install the patch can protect their systems by removing the script mappings for .idq and .ida files via the Internet Services Manager in IIS.
However, as discussed in detail in the FAQ, it is possible for these mappings
to be automatically reinstated if additional system components are added or removed. Because of this, Microsoft recommends that all customers using IIS install the patch, even if the script mappings have been removed. 

Mitigating Factors:
====================
 - The vulnerability can only be exploited if a web session 
   can be established with an affected server. Customers 
   who have installed Index Server or Index Services but not
   IIS would not be at risk. This is the default case for 
   Windows 2000 Professional. 
 - The vulnerability cannot be exploited if the script mappings 
   for Internet Data Administration (.ida) and Internet Data 
   Query (.idq) files are not present. The procedure for 
   removing the mappings is discussed in the IIS 4.0 
   (http://www.microsoft.com/technet/security/iischk.asp) and IIS
   5.0 (http://www.microsoft.com/technet/security/iis5chk.asp)
   Security checklists, can be automatically removed via either 
   the High Security Template or the Windows 2000 Internet Server 
   Security Tool  (http://www.microsoft.com/technet/security/tools.asp). 
   Customers should be aware, however, that subsequently adding 
   or removing system components can cause the mapping to be 
   reinstated, as discussed in the FAQ. 
 - An attacker's ability to extend control from a compromised web
   server to other machines would depend heavily on the specific
   configuration of the network. Best practices recommend that the
   network architecture account for the inherent high-risk that 
   machines in an uncontrolled environment, like the Internet, 
   face by minimizing overall exposure though measures like DMZ's,
   operating with minimal services and isolating contact with 
   internal networks. Steps like this can limit overall exposure
   and impede an attacker's ability to broaden the scope of a 
   possible compromise. 

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-033.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - eEye Digital Security (http://www.eeye.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 
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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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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
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