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Title:      HyperTerminal Buffer Overflow Vulnerability
Released:   18 October 2000
Revised:    24 May 2001 (version 2.0)
Software:   HyperTerminal on Windows 98, 98SE, Windows ME, 
              Windows NT 4.0, Windows 2000
Impact:     Privilege Elevation
Bulletin:   MS00-079

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS00-079.asp.
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Reason for Revision:
====================
Microsoft has re-released this bulletin to inform customers of the
availability of an updated set of patches to address both the
original and a second vulnerability identified in HyperTerminal. 
Information about the second issue is discussed in the Issue section
below and in the security bulletin referenced above.

Issue:
======
The HyperTerminal application is a communications utility that
installs by default on all versions of Windows 98, 98SE, Windows ME,
Windows NT 4.0, and Windows 2000. The product contains two unchecked
buffers through which an attacker could potentially cause code of her
choice to run on another user's machine:

 - One resides in a section of the code that processes Telnet URLs.
If a user opened an HTML mail that contained a particular type of
malformed Telnet URL, and HyperTerminal were configured as the
default Telnet client, it would trigger the buffer overrun.
HyperTerminal is the default Telnet client on Windows 98, 98SE and
ME. It is not the default Telnet client on Windows 2000. 

 - The other resides in a section of the code that processes session
files - files that enable HyperTerminal users to specify session
parameters such as the connection method and the destination host. If
a user opened a session file that contained a particular type of
malformed information, it would trigger the buffer overrun.

Although HyperTerminal ships as part of several Microsoft products,
it was developed by a third party. Additional information on the
vulnerability and a patch for their full version product,
HyperTerminal Private Edition, is available from their web site at
www.hilgraeve.com

Mitigating Factors:
====================
The malicious user must entice another user into clicking on a
specially-formed telnet URL or opening a malformed HyperTerminal
session file.

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms00-079.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - Luciano Martins of USSR Labs (www.ussrback.com) 
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