The following is a Security  Bulletin from the Microsoft Product Security

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Microsoft Security Bulletin (MS99-038)

--------------------------------------



Patch Available for "Spoofed Route Pointer" Vulnerability

Originally Posted: September 20, 1999



Summary

=======

Microsoft has released a patch that eliminates a vulnerability in

Microsoft(r) Windows(r) 95, 98  and Windows NT(r) 4.0 that could allow

source routing to be performed, even if it has ostensibly  been disabled.

The patch also includes added functionality to provide additional control

over  source routing.



Frequently asked questions regarding this vulnerability can be found at

http://www.microsoft.com/security/bulletins/ms99-038faq.asp



Issue

=====

Windows NT 4.0 Service Pack 5 introduced the ability to disable source

routing on a multi-homed  Windows NT machine that acts as a router. However,

even if source routing is disabled, it is  possible to bypass it by

including a specific type of incorrect information within the route  pointer

in the data packet. Windows 95 and 98 also provide this capability, and are

affected by  the same vulnerability. The patch restores correct operation to

the anti-source routing feature.  In addition, it provides additional

functionality that enables source routing to be disabled on  single-homed

machines and on multi-homed machines that are not used as routers.



Customers who are using multi-homed Windows 95, 98 or or Windows NT

machines, and who  wish to disable source routing should apply the patch to

ensure proper operation of the  anti-source routing features. In addition,

customers who have non-routing machines in vulnerable  locations (for

example, single-homed machines outside of a firewall or multi-homed machines

joining two subnets) may wish to install the patch in order to use the new

functionality to  disable source routing in these cases as well.



Affected Software Versions

==========================

 - Microsoft Windows 95

 - Microsoft Windows 98

 - Microsoft Windows 98 Second Edition

 - Microsoft Windows NT Workstation 4.0

 - Microsoft Windows NT Server 4.0

 - Microsoft Windows NT Server 4.0, Enterprise Edition

 - Microsoft Windows NT Server 4.0, Terminal Server Edition



Patch Availability

==================

 - Windows 95, 98 and Windows 98 Second Edition:

   To be released shortly

 - Windows NT 4.0 Workstation, Windows NT 4.0 Server and Windows

   NT 4.0 Server, Enterprise Edition:

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/

   usa/nt40/Hotfixes-PostSP5/Spoof-fix

 - Windows NT 4.0 Server, Terminal Server Edition:

   To be released shortly



   NOTE: Line breaks have been inserted into the URLs above for readability



More Information

================

Please see the following references for more information related to this

issue.

 - Microsoft Security Bulletin MS99-038: Frequently Asked Questions,

   http://www.microsoft.com/security/bulletins/ms99-038faq.asp.

 - Microsoft Knowledge Base (KB) article Q238453,

   Pointer in Source Route Option Bypasses Source Routing Disable,

   http://support.microsoft.com/support/kb/articles/q238/4/53.asp.

   (Note: It may take 24 hours from the original posting of this

   bulletin for the KB article to be visible.)

 - Microsoft Security Advisor web site,

   http://www.microsoft.com/security/default.asp.



Obtaining Support on this Issue

===============================

This is a fully supported patch. Information on contacting Microsoft

Technical Support is available at

http://support.microsoft.com/support/contact/default.asp.



Acknowledgments

===============

Microsoft acknowledges Network Associates, Inc. (http://www.nai.com) for

bringing this issue to  our attention and working with us to alert customers

about it.



Revisions

=========

 - September 20, 1999: Bulletin Created.



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