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                     National Cyber Alert System

               Technical Cyber Security Alert TA08-297A


Microsoft Windows Server Service RPC Vulnerability

   Original release date: October 23, 2008
   Last revised: --
   Source: US-CERT


Systems Affected

     * Microsoft Windows 2000
     * Microsoft Windows XP
     * Microsoft Windows Server 2003
     * Microsoft Windows Vista
     * Microsoft Windows Server 2008


Overview

   A vulnerability in the way the Microsoft Windows server service
   handles RPC requests  could  allow  an unauthenticated, remote
   attacker to execute arbitrary code with SYSTEM privileges.


I. Description

   Microsoft has released Microsoft Security Bulletin MS08-067 to
   address a buffer  oveflow  vulnerability  in  the  Windows  Server
   service. The vulnerability is caused by a flaw in the way the
   Server service handles Remote Procedure Call (RPC) requests. For
   systems running Windows 2000, XP, and Server 2003, a remote,
   unauthenticated attacker could exploit this vulnerability. For
   systems running Windows Vista and Server 2008, a remote attacker
   would most likely need to authenticate.

   Microsoft Security Bulletin MS08-067 rates this vulnerability as
   "Critical" for Windows 2000, XP, and Server 2003. The bulletin also
   notes "...limited, targeted attacks attempting to exploit the
   vulnerability."

   This vulnerability has been assigned CVE-2008-4250. Further
   information is available in a Security Vulnerability & Research
   blog entry and US-CERT Vulnerability Note VU#827267.


II. Impact

   A remote, unauthenticated attacker could execute arbitrary code or
   cause a vulnerable  system to crash. Since the Server service runs
   with SYSTEM privileges, an attacker could take complete control of
   a vulnerable system.


III. Solution

Apply update

   Microsoft has provided updates for this vulnerability in Microsoft
   Security Bulletin MS08-067. Microsoft also provides security
   updates through the Microsoft Update web site and Automatic
   Updates. System administrators should  consider using an automated
   update distribution system such as Windows Server Update Services
   (WSUS).

Disable Server and Computer Browser services

   Disable the Server and Computer Browser services on Windows systems
   that do not require those services. A typical Windows client that
   is not sharing files or printers is unlikely to need either the
   Server or Computer Browser services. As a best security practice,
   disable all unnecessary services.

Restrict access to server service

   Restrict access to the server service (TCP ports 139 and 445). As a
   best security practice, only allow access to necessary network
   services.

Filter affected RPC identifier

   The host firewalls in Windows Vista and Windows Server 2008 can
   selectively filter RPC Universally Unique Identifiers (UUID). See
   Microsoft Security Bulletin MS08-067 for instructions to filter RPC
   requests with the UUID equal to 
   4b324fc8-1670-01d3-1278-5a47bf6ee188.


IV. References

     * US-CERT Vulnerability Note VU#827267 -
       <http://www.kb.cert.org/vuls/id/827267>

     * Microsoft Security Bulletin MS08-067 -
       <http://www.microsoft.com/technet/security/Bulletin/
       ms08-067.mspx>

     * Microsoft Update - <https://update.microsoft.com/>

     * Windows Update: Automatic Update
       <http://www.microsoft.com/windows/downloads/windowsupdate/
       automaticupdate.mspx>

     * Windows Server Update Services (WSUS) Home -
       <http://technet.microsoft.com/en-us/wsus/default.aspx>

     * CVE-2008-4250 -
       <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4250>

     * More detail about MS08-067, the out-of-band netapi32.dll
       security update -
       <http://blogs.technet.com/swi/archive/2008/10/23/
       More-detail-about-MS08-067.aspx>


 ____________________________________________________________________

   The most recent version of this document can be found at:

     <http://www.us-cert.gov/cas/techalerts/TA08-297A.html>
 ____________________________________________________________________

   Feedback can be directed to US-CERT Technical Staff. Please send
   email to <cert@cert.org> with "TA08-297A Feedback VU#827267" in
   the subject.
 ____________________________________________________________________

   For instructions on subscribing to or unsubscribing from this
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 ____________________________________________________________________

   Produced 2008 by US-CERT, a government organization.

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     <http://www.us-cert.gov/legal.html>
 ____________________________________________________________________


Revision History

   October 23, 2008: Initial release

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