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Microsoft Security Bulletin (MS99-038)
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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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