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Subject: CERT Advisory CA-2003-03 Buffer Overflow in Windows Locator Service
From: CERT Advisory <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Date: Thu, 23 Jan 2003 16:20:34 -0500


CERT Advisory CA-2003-03 Buffer Overflow in Windows Locator Service

   Original issue date: January 23, 2003
   Last revised: --
   Source: CERT/CC

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

Systems Affected

     * Microsoft Windows NT 4.0
     * Microsoft Windows NT 4.0, Terminal Server Edition
     * Microsoft Windows 2000
     * Microsoft Windows XP


   A  buffer  overflow  vulnerability  in  the  Microsoft Windows Locator
   service  could  allow  a  remote attacker to execute arbitrary code or
   cause the Windows Locator service to fail. This service is enabled and
   running  by  default on Windows 2000 domain controllers and Windows NT
   4.0 domain controllers.

I. Description

   A  buffer overflow in the Windows Locator service may make it possible
   for a remote attacker to execute arbitrary code on a vulnerable system
   by  sending  an  overly  large request to the Windows Locator service.
   Microsoft  describes  the  Windows  Locator service as "a name service
   that maps logical names to network-specific names." From MS03-001: 
     A  client  that  is going to make a Remote Procedure Call (RPC) can
     call  the  Locator  service to resolve a logical name for a network
     object  to a network-specific name for use in the RPC. For example,
     if  a  print  server  has  the  logical name "laserprinter", an RPC
     client   could   call   the   Locator   service  to  find  out  the
     network-specific name that mapped to "laserprinter". The RPC client
     uses  the  network-specific  name when it makes the RPC call to the

   Further information about this vulnerability can be found in Microsoft
   Security Bulletin MS03-001 and in CERT/CC Vulnerability Note VU#610986, 
   which correspond to CVE candidate CAN-2003-0003.

II. Impact

   A  remote  attacker  may  be  able  to  execute  arbitrary  code  on a
   vulnerable  system,  or  cause the Windows Locator service to fail. An
   attacker  who  is able to compromise a domain controller might be able
   to  cause  the  compromised  domain controller to trust the attacker's

III. Solution

Apply a patch

Disable vulnerable service

   Until  a  patch  can  be  applied, you may wish to disable the Windows
   Locator  service.  To  determine  if  the  Windows  Locator service is
   running, Microsoft recommends the following:

     * The  status  of  the "Remote Procedure Call (RPC) Locator" service
       and how it is started (automatically or manually) can be viewed in
       the  Control  Panel.  For Windows 2000 and Windows XP, use Control
       Panel  |  Administrative  Tools | Services, and on Windows NT 4.0,
       use Control Panel | Services.

     * It is also possible to determine the status of the Locator service
       from the command line by entering: net start

     * A  list  of  services will be displayed. If "Remote Procedure Call
       (RPC)  Locator"  appears  in the list, then the locator service is

   To  disable  the  Windows  Locator  service,  Microsoft recommends the

     * An  administrator  can  disable the Locator service by setting the
       RpcLocator  service  status  to "disabled" in the services control

     * The  service  can  also  be stopped via the command line using the
       sc.exe  program,  which  ships  with Windows XP and is included as
       part  of the Windows 2000 Resource Kit. The following command will
       stop the service: sc stop RpcLocator

     * To  disable  the  service  using  the  command  line tool, use the
       following: sc config RpcLocator start= disabled

Restrict access to NetBIOS

   You  may  wish  to  block  access to NetBIOS from outside your network
   perimeter. This will limit your exposure to attacks. However, blocking
   at  the  network  perimeter  would  still  allow  attackers within the
   perimeter  of  your  network  to  exploit  the  vulnerability.  It  is
   important  to  understand  your  network's  configuration  and service
   requirements before deciding what changes are appropriate.

   As a best practice, the CERT/CC recommends disabling all services that
   are  not  explicitly  required. Before deciding to disable the Windows
   Locator  service, carefully consider your service requirements. Please
   also  note  that  Microsoft is actively deploying the patches for this
   vulnerability via Windows Update.

Appendix A. Vendor Information

   This  appendix  contains information provided by vendors. When vendors
   report  new  information,  this section is updated and the changes are
   noted  in  the  revision  history. If a vendor is not listed below, we
   have not received their comments.

Microsoft Corporation

     Please see Microsoft Security Bulletin MS03-001.

Appendix B. References

     * Microsoft Security Bulletin MS03-001 -

     * CERT/CC Vulnerability Note VU#10986 -

   This   vulnerability  was  discovered  by  David  Litchfield  of  Next
   Generation Security Software Ltd and was first described in MS03-001.

   Author: Ian A. Finlay.

   This document is available from:

CERT/CC Contact Information

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   Revision History

   January 23, 2003: Initial release

Version: PGP 6.5.8


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