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Q230677: Malformed Phonebook Entry Security Vulnerability in RAS Client

Article: Q230677
Product(s): Microsoft Windows NT
Version(s): winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Operating System(s): 
Keyword(s): kbWinNT4sp6fix
Last Modified: 16-MAY-2002

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The information in this article applies to:

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

Microsoft Remote Access Service (RAS) client software may allow a user with the
proper permissions to mount a denial-of-service attack or elevate his or her
privileges on a RAS client computer.

CAUSE
=====

This behavior occurs because the RAS client component that processes phonebook
entries has an unchecked buffer. As a result, a specially malformed RAS
phonebook entry can cause the RAS client to crash.

In very specific conditions, it can cause arbitrary code to run on the client
computer. Because the RAS client operates in the security context of the local
computer, the arbitrary code also runs in this context. This cannot occur
accidentally.

RESOLUTION
==========

Windows NT Server or Workstation 4.0
------------------------------------

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the
individual software update. For information on obtaining the latest service
pack, please go to:

- http://www.microsoft.com/Windows/ServicePacks/

-or-

- Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft
Product Support Services. 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


Windows NT Server 4.0, Terminal Server Edition
----------------------------------------------

To resolve this problem, obtain the latest service pack for Windows NT Server
4.0, Terminal Server Edition. For additional information, please see the
following article in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack



STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products that are
listed at the beginning of this article. This problem was first corrected in
Windows NT Server version 4.0, Terminal Server Edition Service Pack 6.

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

This vulnerability affects only computers running the RAS client software; it
does not affect RAS servers. A user must have permission to add or modify
phonebook entries to initiate an attack. Permissions can be set using the
phonebook's access control list (ACL).

Computers at risk because of this vulnerability are workstations that are
configured to dial other computers as servers, including Microsoft Windows NT
4.0, Terminal Server Edition, but are not typically configured to act as RAS
clients. This vulnerability affects only local computers; a user cannot directly
attack remote computers.

For additional security-related information about Microsoft products, please
visit the following Microsoft Web site:

  http://www.microsoft.com/security/

Additional query words:

======================================================================
Keywords          : kbWinNT4sp6fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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