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Title: Flaw in Windows Me Help and Support Center Could
Enable Code Execution (812709)
Date: 26 February, 2003
Software: Microsoft Windows Me
Impact: Run Code of Attacker's Choice
Max Risk: Critical
Bulletin: MS03-006

Microsoft encourages customers to review the Security Bulletins
at:
http://www.microsoft.com/technet/security/bulletin/MS03-006.asp
http://www.microsoft.com/security/security_bulletins/ms03-006.asp

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Issue:

Help and Support Center provides a centralized facility through
which users can obtain assistance on a variety of topics. For
instance, it provides product documentation, assistance in
determining hardware compatibility, access to Windows Update,
online help from Microsoft, and other assistance. Users and
programs can execute URL links to Help and Support Center by
using the "hcp://" prefix in a URL link instead of "http://".

A security vulnerability is present in the Windows Me version of
Help and Support Center, and results because the URL Handler for
the "hcp://" prefix contains an unchecked buffer.

An attacker could exploit the vulnerability by constructing a URL
that,when clicked on by the user, would execute code of the
attacker's choice in the Local Computer security context. The URL
could be hosted on a web page, or sent directly to the user in
email. In the web based scenario, where a user then clicked on
the URL hosted on a website, an attacker could have the ability
to read or launch files already present on the local machine. In
the case of an e-mail borne attack, if the user was using Outlook
Express 6.0 or Outlook 2002 in their default configurations, or
Outlook 98 or 2000 in conjunction with the Outlook Email Security
Update, then an attack could not be automated and the user would
still need to click on a URL sent in e-mail. However if the user
was not using Outlook Express 6.0 or Outlook 2002 in their
default configurations, or Outlook 98 or 2000 in conjunction with
the Outlook Email Security Update, the attacker could cause an
attack to trigger automatically without the user having to click
on a URL contained in an e-mail.

Mitigating Factors:

• The Help and Support Center function could not be started
  automatically in Outlook Express or Outlook if the user is
  running Internet Explorer 6.0 Service Pack 1.
• For an attack to be successful, the user would need to visit a
  website under the attacker's control or receive an HTML e-mail
  from the attacker.
• Automatic exploitation of the vulnerability by an HTML email
  would be blocked by Outlook Express 6.0 and Outlook 2002 in their
  default configurations, and by Outlook 98 and 2000 if used in
  conjunction with the Outlook Email Security Update.

Risk Rating:

• Critical

Patch Availability:

• A patch is available to fix this vulnerability. Please read
  the Security Bulletins at

http://www.microsoft.com/technet/security/bulletin/ms03-006.asp
http://www.microsoft.com/security/security_bulletins/ms03-006.asp

for information on obtaining this patch.

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ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL
OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

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