[SECURITY-L] [0_47374_AEE7C282-5BFD-4E84-98BC-79A14F27B03B_BR em Newsletters.Microsoft.com: Revised: Microsoft Security Bulletin MS02-071: Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation(328310)]

Seg Maio 5 09:48:54 -03 2003

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From: "Microsoft" <0_47374_AEE7C282-5BFD-4E84-98BC-79A14F27B03B_BR em Newsletters.Microsoft.com>
Subject: Revised: Microsoft Security Bulletin MS02-071: Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation (328310)
To: <mieko em ccuec.unicamp.br>
Date: Wed, 30 Apr 2003 23:30:55 -0700
X-Mailer: Microsoft CDO for Windows 2000

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Title:      Flaw in Windows WM_TIMER Message Handling Could          
            Enable Privilege Elevation (328310)
Released:   December 11, 2002
Revised:    April 30, 2003 (version 3.0)
Software:   Microsoft(r) Windows(r) NT 4.0, Windows 2000, and Windows
            XP
Impact:     Privilege elevation 
Max Risk:   Important 

Bulletin:   MS02-071

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS02-071.asp
http://www.microsoft.com/security/security_bulletins/ms02-071.asp
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Reason for Revision:
====================

Subsequent to the release of this patch Microsoft identified a 
problem affected Windows NT 4.0 TSE multi processor systems which 
was causing them to fail. The patch should have been installable 
on both single and multi processor system and the installer 
should have copied the correct binaries onto the system depending 
on whether the system was single or multi processor. However an 
installer error meant that the correct binaries were not being 
copied onto multi processor systems, causing them to fail under 
certain scenarios. Microsoft has updated the patch for Windows NT 
4.0 TSE to correct this error. It should be noted that this patch 
only corrects an installer problem with multi processor Windows 
NT 4.0 TSE systems - there is no requirement to re-install the 
patch on single processor systems as the installer functions 
correctly on those systems.

Issue:
======

Subsequent to the release of this bulletin it was determined that 
the patch for Microsoft Windows NT 4.0 machines introduced an 
error that could, under certain configurations, cause NT 4.0 to 
fail. Microsoft has investigated this issue and has released an 
updated patch for Windows NT 4.0. The bulletin has been updated 
to include the new download links for the NT 4.0 patch. The error 
did not affect NT 4.0 TSE, except for the Japanese Language. 
Customers running the Japanese version of NT 4.0 TSE should apply 
the updated fix. 

Customers who have installed the patch on Microsoft Windows 2000 
and Windows XP are unaffected by this error. 
Windows messages provide a way for interactive processes to react 
to user events (e.g., keystrokes or mouse movements) and 
communicate with other interactive processes. One such message, 
WM_TIMER, is sent at the expiration of a timer, and can be used 
to cause a process to execute a timer callback function. A 
security vulnerability results because it's possible for one 
process in the interactive desktop to use a WM_TIMER message to 
cause another process to execute a callback function at the 
address of its choice, even if the second process did not set a 
timer. If that second process had higher privileges than the 
first, this would provide the first process with a way of 
exercising them. 

By default, several of the processes running in the interactive 
desktop do so with LocalSystem privileges. As a result, an 
attacker who had the ability to log onto a system interactively 
could potentially run a program that would levy a WM_TIMER 
request upon such a process, causing it to take any action the 
attacker specified. This would give the attacker complete control 
over the system. 
In addition to addressing this vulnerability, the patch also 
makes changes to several processes that run on the interactive 
desktop with high privileges. Although none of these would, in 
the absence of the TM_TIMER vulnerability, enable an attacker to 
gain privileges on the system, we have included them in the patch 
to make the services more robust.  

Mitigating Factors:
====================
- -An attacker would need valid logon credentials to exploit the 
vulnerability. It could not be exploited remotely. 
- -Properly secured servers would be at little risk from this 
vulnerability. Standard best practices recommend only allowing 
trusted administrators to log onto such systems interactively; 
without such privileges, an attacker could not exploit the 
vulnerability.

Risk Rating:
============
Important

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletins at

   http://www.microsoft.com/technet/security/bulletin/ms02-071.asp
   http://www.microsoft.com/security/security_bulletins/ms02-071.asp

   for information on obtaining this patch.

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