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Title: Unchecked Buffer in Windows Shell Could Enable System
Compromise (329390)
Date: 18 December 2002
Software: Microsoft Windows XP
Impact: Run code of an attacker's choice
Max Risk: Critical
Bulletin: MS02-072

Microsoft encourages customers to review the Security Bulletins at:
http://www.microsoft.com/technet/security/bulletin/MS02-072.asp
http://www.microsoft.com/security/security_bulletins/ms02-072.asp

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Issue:

The Windows Shell is responsible for providing the basic framework
of the Windows user interface experience. It is most familiar to
users as the Windows Desktop, but also provides a variety of other
functions to help define the user's computing session, including
organizing files and folders, and providing the means to start
applications.

An unchecked buffer exists in one of the functions used by the
Windows Shell to extract custom attribute information from audio
files. A security vulnerability results because it is possible
for a malicious user to mount a buffer overrun attack and attempt
to exploit this flaw.

An attacker could seek to exploit this vulnerability by creating
an .MP3 or .WMA file that contained a corrupt custom attribute
and then host it on a website, on a network share, or send it via
an HTML email. If a user were to hover his or her mouse pointer
over the icon for the file (either on a web page or on the local
disk), or open the shared folder where the file was stored, the
vulnerable code would be invoked. An HTML email could cause the
vulnerable code to be invoked when a user opened or previewed the
email. A successful attack could have the effect of either causing
the Windows Shell to fail, or causing an attacker's code to run on
the user's computer in the security context of the user.

Mitigating Factors:

• The vulnerability lies in the Windows Shell, rather than Windows
  Media Player. As a result, playing an audio file with Windows
  Media Player would not pose any additional risk.

• Outlook 98 and 2000 (after installing the Outlook Email Security
  Update),Outlook 2002, and Outlook Express 6 all open HTML mail in
  the Restricted Sites Zone. Customers who are using these products
  and who have also installed Windows XP Service Pack 1 or any
  recent security patch for Internet Explorer that disables frames
  in the Restricted Sites zone would not be at risk from automated
  email-borne attacks. However, these customers could still be
  attacked if they choose to click on a hyperlink in a malicious
  HTML email.

• In the case where an attacker's code was executed, the code
  would run in the security context of the user. As a result,
  any limitations on the user's ability would also restrict the
  actions that an attacker's code could take.

Risk Rating:

• Windows XP: Critical

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin at
  http://www.microsoft.com/technet/security/bulletin/ms02-072.asp
  for information on obtaining this patch.

Acknowledgment:

• Foundstone Research Labs (http://www.foundstone.com)

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