Microsoft Security Bulletin (MS99-057)

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Microsoft Security Bulletin (MS99-057)
--------------------------------------

Patch Available for "Malformed Security Identifier Request" Vulnerability
Originally Posted: December 16, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability in
Microsoft(r) Windows NT(r) 4.0.  The vulnerability could allow a malicious
user to cause a Windows NT machine to stop responding  to requests for
service. The patch for this vulnerability is included in the
previously-released  patch for the "Syskey Keystream Reuse" vulnerability;
customers who have already applied it do  not need to take any further
action.

Frequently asked questions regarding this vulnerability can be found at
http://www.microsoft.com/security/bulletins/MS99-057faq.asp.

Issue
=====
The Windows NT Local Security Authority (LSA) provides a number of functions
for enumerating and  manipulating security information. One of these
functions, LsaLookupSids(), is used to determine  the Security Identifier
(SID) associated with a particular user or group name. A flaw in the
implementation of this function causes it to incorrectly handle certain
types of invalid  arguments. If an affected call were made to this function,
it would cause the LSA to crash,  thereby preventing the machine from
performing useful work.

An affected machine could be put back into service by rebooting, with the
loss of any work that  was in progress at the time. Remote attacks via this
vulnerability would not be possible if  NetBios is filtered at the firewall.

Affected Software Versions
==========================
 - 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
==================

 - This fix for this vulnerability is included in the patch
   for the "Syskey Keystream Reuse" vulnerability. (See
   http://www.microsoft.com/Security/Bulletins/ms99-056.asp for
   more information on this vulnerability).  Customers who
   have already applied it do not need to take any additional action.

NOTE: Additional security patches are available at the Microsoft Download
Center

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-057: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-057faq.asp.
 - Microsoft Knowledge Base (KB) article Q248185,
   SID Enumeration Function in LSA may not Handle Argument Properly,
   http://support.microsoft.com/support/kb/articles/q248/1/85.asp.
   (Note: It may take 24 hours from the original posting of this bulletin
   for this KB article to be visible.)
 - Microsoft Security Bulletin MS99-056:
   Patch Available for "Syskey Keystream Reuse" Vulnerability,
   http://www.microsoft.com/Security/Bulletins/ms99-056.asp.
 - 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 Anthony Osborne of the Security Labs of Network
Associates for bringing  this issue to our attention.

Revisions
=========
 - December 16, 1999: Bulletin Created.

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