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Microsoft Security Bulletin (MS99-047)
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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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