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

   Original release date: June 19, 2001
   Last revised: August 16, 2001
   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
       enabled
     * Systems running Microsoft Windows 2000 (Professional, Server,
       Advanced Server, Datacenter Server)
     * Systems running beta versions of Microsoft Windows XP
       
Overview

   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
   possible.
   
   A translation of this advisory into Polish is available at
   http://www.cert.pl/CA/CA-2001-13-PL.html.
   
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:
   
          http://www.microsoft.com/technet/security/bulletin/MS01-033.asp
          
   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
   MS01-033:

   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:
   
          http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0500
          
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:
   
          http://www.microsoft.com/Downloads/Release.asp?ReleaseID=30833
          
   For Windows 2000 Professional, Server, and Advanced Server:
   
          http://www.microsoft.com/Downloads/Release.asp?ReleaseID=30800 
          
   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:
   
          http://www.microsoft.com/windows2000/datacenter/howtobuy/purcha
          sing/oems.asp
          
Workarounds

   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
   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:
   
          http://www.microsoft.com/technet/security/bulletin/MS01-033.asp
          
   http://www.microsoft.com/technet/security/bulletin/MS01-044.asp
   
          http://www.microsoft.com/technet/support/kb.asp?ID=Q300972
          
References

    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,
       https://www.kb.cert.org/vuls/id/952336
    2. Additional advice on securing IIS web servers is available from
       
                http://www.microsoft.com/technet/security/iis5chk.asp
                http://www.microsoft.com/technet/security/tools.asp
                
   Feedback concerning this document may be directed to Jeffrey S.
   Havrilla.
   ______________________________________________________________________
   
   This document is available from:
   http://www.cert.org/advisories/CA-2001-13.html
   ______________________________________________________________________
   
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   Revision History
Jun 19, 2001: Initial Release
Jun 21, 2001: Removed statement about patch supersession
Jul 17, 2001: Updated Feedback link
Jul 30, 2001: Added link to Polish translation
Aug 16, 2001: Added link to Microsoft Security Bulletin MS01-044