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Q305399: Malformed Request to RPC Endpoint Mapper can Cause RPC Service t

Article: Q305399
Product(s): Microsoft Windows NT
Version(s): 4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
Operating System(s): 
Keyword(s): kbSecurity kbWinNT400PreSP7Fix
Last Modified: 12-JUN-2002

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The information in this article applies to:

- Microsoft Windows NT Server versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4, 4.0 SP5, 4.0 SP6a 
- Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6a 
- Microsoft Windows NT Workstation versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4, 4.0 SP5, 4.0 SP6a 
- Microsoft Windows NT Server versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6, Terminal Server Edition 
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SYMPTOMS
========

The RPC (Remote Procedure Call) endpoint mapper allows RPC clients to determine
the port number currently assigned to a particular RPC service. Because the
endpoint mapper runs within the RPC service itself, exploiting this
vulnerability would cause the RPC service itself to fail, with the attendant
loss of any RPC-based services the server offers, as well as potential loss of
some COM functions. Normal service could be restored by rebooting the system.

Standard security recommendations call for port 135 (the port on which the RPC
endmapper operates) to be blocked at the firewall. If this were done, the chief
threat posed by this vulnerability would be from internal attacks.

CAUSE
=====

This vulnerability results because the Windows NT 4.0 Remote Procedure Call
(RPC) service will fail if the endpoint mapper is sent a request that contains a
particular type of malformed data.

RESOLUTION
==========

A supported fix is now available from Microsoft, but it is only intended to
correct the problem described in this article and should be applied only to
systems that are determined to be at risk of attack. Please evaluate your
computer's physical accessibility, network and Internet connectivity, and other
factors to determine the degree of risk to your computer. Please see the
associated Microsoft Security Bulletin
(http://www.microsoft.com/technet/security/bulletin/ms01-048.asp) to help make
this determination. This fix may receive additional testing at a later time, to
further ensure product quality. If your computer is sufficiently at risk,
Microsoft recommends that you apply this fix now.

To resolve this problem immediately, download the fix as instructed below or
contact Microsoft Product Support Services to obtain the fix. For a complete
list of Microsoft Product Support Services phone numbers and information on
support costs, please go to the following address on the World Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are normally incurred for support calls may
be canceled, if a Microsoft Support Professional determines that a specific
update will resolve your problem. Normal support costs will apply to additional
support questions and issues that do not qualify for the specific update in
question.

The following file is available for download from the Microsoft Download Center:

  DownloadDownload Q305399i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=32503)

  NOTE: A patch for Windows NT Server 4.0, Terminal Server Edition is
  forthcoming.

Release Date: September 10, 2001

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. After it is posted, the file is housed on
secure servers that prevent any unauthorized changes to the file.

The English version of this fix should have the following file attributes or
later:

  Date         Time   Version        Size     File name
  ------------------------------------------------------
  09-Aug-2001  10:56  4.0.1381.7097  701,200  Ole32.dll
  09-Aug-2001  10:56  4.0.1381.7097  343,312  Rpcrt4.dll
  16-Aug-2001  12:01  4.0.1381.7097  107,280  Rpcss.exe

NOTE: Due to file dependencies, this hotfix requires Microsoft Windows NT 4.0
Service Pack 6a (SP6a).



STATUS
======

Microsoft has confirmed that this problem could result in some degree of
security vulnerability in Windows NT 4.0.

MORE INFORMATION
================

For more information on this vulnerability, see the following Microsoft Web
site:

  http://www.microsoft.com/technet/security/bulletin/ms01-048.asp

Additional query words: security_patch DoS denial of service

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Keywords          : kbSecurity kbWinNT400PreSP7Fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTW400sp5 kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp5 kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServ400sp4 kbNTTermServ400sp5 kbNTTermServ400sp6 kbNTTermServSearch kbWinNTSEnt400SP6a kbWinNTW400SP6a
Version           : :4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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