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                     National Cyber Alert System

               Technical Cyber Security Alert TA06-139A


Microsoft Word Vulnerability

   Original release date: May 19, 2006
   Last revised: --
   Source: US-CERT


Systems Affected

     * Microsoft Word 2003
     * Microsoft Word XP (2002)

   Microsoft Word is included in Microsoft Works Suite and Microsoft
   Office. Other versions of Word, and other Office programs may be
   affected or act as attack vectors.


Overview

   A buffer overflow vulnerability in Microsoft Word could allow an
   attacker to execute arbitrary code on a vulnerable system.


I. Description

   Microsoft Word contains a buffer overflow vulnerability. Opening a
   specially crafted Word document, including documents hosted on web
   sites or attached to email messages, could trigger the
   vulnerability.

   Office documents can contain embedded objects. For example, a
   malicious Word document could be embedded in an Excel or PowerPoint
   document. Office documents other than Word documents could be used
   as attack vectors.

   For more information, please see Vulnerability Note VU#446012.


II. Impact

   By convincing a user to open a specially crafted Word document, an
   attacker could execute arbitrary code on a vulnerable system. If
   the user has administrative privileges, the attacker could gain
   complete control of the system.


III. Solution

   At the time of writing, there is no complete solution available.
   Consider the following workarounds:

   Do not open untrusted Word documents

    Do not open unfamiliar or unexpected Word or other Office
    documents, including those received as email attachments or hosted
    on a web site.  Please see Cyber Security Tip ST04-010 for more
    information.

   Do not rely on file extension filtering

    In most cases, Windows will call Word to open a document even if
    the document has an unknown file extension. For example, if
    document.d0c (note the digit "0") contains the correct file header
    information, Windows will open document.d0c with Word.


Appendix A. References

     * Vulnerability Note VU#446012 -
       <http://www.kb.cert.org/vuls/id/446012>

     * Cyber Security Tip ST04-010 -
       <http://www.us-cert.gov/cas/tips/ST04-010.html>


 ____________________________________________________________________

   Information used in this document came from SANS and Microsoft.
 ____________________________________________________________________

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

     <http://www.us-cert.gov/cas/techalerts/TA06-139A.html>
 ____________________________________________________________________

   Feedback can be directed to US-CERT Technical Staff. Please send
   email to <cert@cert.org> with "TA06-139A Feedback VU#446012" in the
   subject.
 ____________________________________________________________________

   For instructions on subscribing to or unsubscribing from this
   mailing list, visit <http://www.us-cert.gov/cas/signup.html>.
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   Produced 2006 by US-CERT, a government organization.

   Terms of use:

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


Revision History

   May 19, 2006: Initial release

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