Microsoft Security Bulletin (MS99-034)

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Microsoft Security Bulletin (MS99-034)
--------------------------------------

Patch Available for "Fragmented IGMP Packet" Vulnerability
Originally Posted: September 03, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability in the TCP/IP
stack  implementations of Microsoft(r) Windows(r) 95, Windows 98 and Windows
NT(r) 4.0. Fragmented IGMP  packets can cause a variety of problems in
Windows 95 and 98, up to and including causing the  machine to crash.
Windows NT 4.0 contains the same vulnerability, but other system mechanisms
make a successful attack much more difficult.

Frequently asked questions regarding this vulnerability can be found at
http://www.microsoft.com/security/bulletins/MS99-034faq.asp

Issue
=====
By sending fragmented IGMP packets to a Windows 95, 98 or Windows NT 4.0
machine, it is possible  to disrupt the normal operation of the machine.
This vulnerability primarily affects Windows 95  and 98 machines. Depending
on a variety of factors, sending such packets to a Windows 95 or 98  machine
may elicit behavior ranging from slow performance to crashing.

Windows NT contains the same vulnerability, but other system mechanisms
compensate and make it  much more difficult to mount a successful attack.

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:
   This patch will be available shortly
 - Windows 98:
   http://www.microsoft.com/windows98/downloads/corporate.asp
 - Windows NT Workstation 4.0; Windows NT Server 4.0;
   Windows NT Server, Enterprise Edition:
   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa
   /NT40/hotfixes-postSP5/IGMP-fix/
 - Windows NT Server 4.0, Terminal Server Edition:
   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa
   /NT40TSE/hotfixes-postSP5/IGMP-fix/

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

   NOTE: The Windows 95 and 98 patches also will be available via
   WindowsUpdate (http://www.microsoft.com/windowsupdate) circa
   September 9, 1999.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-034: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-034faq.asp.
 - Microsoft Knowledge Base (KB) article Q238329,
   Fragmented IGMP Packets may Promote Denial of Service,
   http://support.microsoft.com/support/kb/articles/q238/3/29.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.

Revisions
=========
 - September 03, 1999: Bulletin Created.

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

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