AUSCERT External Security Bulletin Redistribution

                 ESB-2001.241 -- CERT Advisory CA-2001-13
                Buffer Overflow In IIS Indexing Service DLL
                               20 June 2001


        AusCERT Security Bulletin Summary

Product:                Microsoft Index Server 2.0
                        Indexing Service in Windows 2000
                        Indexing Service in Windows XP beta
Vendor:                 Microsoft
Operating System:       Microsoft Windows NT 4.0 with IIS 4.0 or IIS 5.0
                        Microsoft Windows 2000 Professional
                        Microsoft Windows 2000 Server
                        Microsoft Windows 2000 Advanced Server
                        Microsoft Windows 2000 Datacenter Server
                        Microsoft Windows XP beta
Impact:                 Execute Arbitrary Code/Commands
                        Administrator Compromise
Access Required:        Remote

Ref:                    ESB-2001.238

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CERT Advisory CA-2001-13 Buffer Overflow In IIS Indexing Service DLL

   Original release date: June 19, 2001
   Last revised: --
   Source: CERT/CC

   A complete revision history is at the end of this file.

Systems Affected

     * Systems running Microsoft Windows NT 4.0 with IIS 4.0 or IIS 5.0
     * Systems running Microsoft Windows 2000 (Professional, Server,
       Advanced Server, Datacenter Server)
     * Systems running beta versions of Microsoft Windows XP


   A vulnerability exists in the Indexing Services used by Microsoft IIS
   4.0 and IIS 5.0 running on Windows NT, Windows 2000, and beta versions
   of Windows XP. This vulnerability allows a remote intruder to run
   arbitrary code on the victim machine.

   Since specific technical details on how to create an exploit are
   publicly available for this vulnerability, system administrators
   should apply fixes or workarounds on affected systems as soon as

I. Description

   There is a remotely exploitable buffer overflow in one of the ISAPI
   extensions installed with most versions of IIS 4.0 and 5.0 (The
   specific Internet/Indexing Service Application Programming Interface
   extension is IDQ.DLL). An intruder exploiting this vulnerability may
   be able to execute arbitrary code in the Local System security
   context. This essentially can give the attacker complete control of
   the victim system.

   This vulnerability was discovered by eEye Digital Security. Microsoft
   has released the following bulletin regarding this issue:


   Affected versions of Windows include Windows NT 4.0 (installed with
   IIS 4.0 and Index Server 2.0), Windows 2000 (Server and Professional
   with IIS 5.0 installed), and Windows 2000 Datacenter Server OEM
   distributions; however, not all of these instances are vulnerable by
   default. The beta versions of Windows XP are vulnerable by default.

   The only precondition for exploiting this vulnerability is that an IIS
   server is running with script mappings for Internet Data
   Administration (.ida) and Internet Data Query (.idq) files. The
   Indexing Services do not need to be running. As stated by Microsoft in

          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.

   This vulnerability has been assigned the identifier CAN-2001-0500 by
   the Common Vulnerabilities and Exposures (CVE) group:


II. Impact

   Anyone who can reach a vulnerable web server can execute arbitrary
   code in the Local System security context. This results in the
   intruder gaining complete control of the system. Note that this may be
   significantly more serious than a simple "web defacement."

III. Solution

Apply a patch from your vendor

   Apply patches for vulnerable Windows NT 4.0 and Windows 2000 systems:

   For Windows NT 4.0:


   For Windows 2000 Professional, Server, and Advanced Server:


   These patches supersede the ones previously provided in Microsoft
   Security Bulletins MS01-025 and MS00-006.

   Users of Windows 2000 Datacenter Server software should contact their
   original equipment manufacturer (OEM) for patches. A list of OEM
   providers may be found here:



   Users of beta copies of Windows XP should upgrade to a newer version
   of the software when it becomes available.

   All affected versions of IIS/Indexing Services can be protected
   against exploits of this vulnerability by removing script mappings for
   for Internet Data Administration (.ida) and Internet Data Query (.idq)
   files. However, such mappings may be recreated when installing other
   related software components.

Appendix A. Vendor Information

Microsoft Corporation

   The following documents regarding this vulnerability are available
   from Microsoft:



    1. VU#952336: Microsoft Index Server/Indexing Service used by IIS
       4.0/5.0 contains unchecked buffer used when encoding double-byte
       characters CERT/CC, 06/19/2001,


    2. Additional advice on securing IIS web servers is available from


   Feedback concerning this document may be directed to Jeffrey S.

   This document is available from:



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   Revision History
Jun 19, 2001: Initial Release

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