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Title:      Patch Available for "Malformed PPTP Packet Stream"
            Vulnerability
Date:       13 February 2001
Software:   Windows NT 4.0 servers running PPTP
Impact:     Denial of service
Bulletin:   MS01-009

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-009.asp.
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Issue:
======
The PPTP service in Windows NT 4.0 has a flaw in a part of the code
that handles a  particular type of data packet, which results in a
leak of kernel memory. If a sufficient  number of packets containing
a specific malformation were received by an affected server,  kernel
memory would eventually become exhausted. The likely outcome would be
that the server  would either hang or fail altogether. In either
case, the machine would need to be rebooted  to restore normal
operation, and any PPTP sessions underway at the time would be lost.
It  would not be necessary for the attacker to establish a valid PPTP
session in order to  exploit the vulnerability.

Mitigating Factors:
====================
 - The vulnerability does not threaten the security of data within
   PPTP sessions -- it is strictly a denial of service vulnerability.
 - Only Windows NT 4.0 machines running the PPTP service are at risk.
   The service does not run by default.
 - The Windows 2000 PPTP service is not affected by the
   vulnerability.

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-009.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - Kirk Corey of Diversified Software Industries, Inc.
   (www.dsi-inc.net)

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