Microsoft Security Bulletin (MS99-047)

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



Patch Available for "Malformed Spooler Request" Vulnerability

Originally Posted: November 04, 1999



Summary

=======

Microsoft has released a patch that eliminates a security vulnerability in

Microsoft(r) Windows  NT(r) 4.0. The vulnerability could allow a user to

cause the print spooler service to crash, or  to run arbitrary code on a

Windows NT machine. The patch also eliminates a vulnerability that  could

allow a user to substitute code of their choosing for a print provider that

runs in a  privileged state.



Frequently asked questions regarding this vulnerability can be found

at http://www.microsoft.com/security/bulletins/MS99-047faq.asp.



Issue

=====

Certain APIs in the Windows NT 4.0 print spooler subsystem have unchecked

buffers. If an affected  API were provided with random data as input, it

could crash the print spooler service. If it were  provided with a

specially-malformed argument, it could be used to run arbitrary code on the

server via a classic buffer overrun attack. The majority of the affected

APIs require the caller  to be a member of the Power Users or Administrators

group; however, at least one is callable by  normal users. None of the calls

could be made by anonymous users, but the calls could be made  remotely.



A second vulnerability exists because incorrect permissions would allow a

normal user to specify  his or her own code as a print provider. Because

print providers run in a local System context,  this would allow the user to

gain additional privileges on the local machine. This vulnerability  could

not be exploited remotely.



Affected Software Versions

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

 - Microsoft Windows NT 4.0 Workstation

 - Microsoft Windows NT 4.0 Server

 - Microsoft Windows NT 4.0 Server, Enterprise Edition

 - Microsoft Windows NT 4.0 Server, Terminal Server Edition



Patch Availability

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

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

Enterprise Edition:

 - X86:

   http://download.microsoft.com/download/winntsrv40/Patch/

   Spooler-fix/NT4/EN-US/Q243649.exe

 - Alpha:

   http://download.microsoft.com/download/winntsrv40/Patch/

   Spooler-fix/ALPHA/EN-US/Q243649.exe



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



   NOTE: The patches above can be installed on systems running Windows

   NT 4.0 Service Pack 5 or 6. A version that can be installed on systems

   running previous service packs will be released shortly.



 - Windows NT 4.0 Server, Terminal Server Edition:

   To be released shortly



More Information

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

Please see the following references for more information related to this

issue.

 - Microsoft Security Bulletin MS99-047: Frequently Asked Questions,

   http://www.microsoft.com/security/bulletins/MS99-047faq.asp.

 - Microsoft Knowledge Base (KB) article Q243649,

   Unchecked Print Spooler Buffer may Expose System Vulnerability,

   http://support.microsoft.com/support/kb/articles/q243/6/49.asp.

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

   for this 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 the eEye Digital Security Team (www.eEye.com/release)

for discovering the  buffer overrun vulnerability and reporting it to us.



Revisions

=========

 - November 04, 1999: Bulletin Created.



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