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CERT Advisory CA-2000-14 Microsoft Outlook and Outlook Express Cache Bypass
Vulnerability
Original release date: July 26, 2000
Source: CERT/CC
A complete revision history is at the end of this file.
Systems Affected
* Any system running Microsoft Outlook Express 4.0 or 4.01
* Any system running Microsoft Outlook Express 5.0 or 5.01
* Any system running Microsoft Outlook 98
* Any system running Microsoft Outlook 2000
Overview
Microsoft has recently released Microsoft Security Bulletin MS00-046,
in which they announced a patch for the "Cache Bypass" vulnerability.
By exploiting this vulnerability, an attacker can use an
HTML-formatted message to read certain types of files on the victim's
machine.
In addition, because this vulnerability also allows the attacker to
store files on the victim's machine, it can be used in conjunction
with existing vulnerabilities to execute arbitrary code on the target
system.
I. Description
"Cache Bypass" Vulnerability
Typically, all files downloaded by either Outlook or Internet Explorer
are stored in an area known as a cache. The cache serves two main
purposes. First, it provides temporary storage for online content,
which minimizes the amount of data that must be transferred when
refreshing a page. Second, it provides an area where Internet content
can be downloaded to the local machine and accessed with the same
security policy as remote content.
This vulnerability allows attackers to use an HTML-formatted message
to store files outside the cache. Inside the cache, the files are
governed by the security policy of the "Internet Zone," but outside
they are governed by the "Local Computer Zone." Once a file is stored
in the "Local Computer Zone," the security policy of the "Internet
Zone" no longer applies to it. This could put systems at risk because
the security policies of the "Local Computer Zone" are typically more
permissive than those of the "Internet Zone."
II. Impact
When exploited, this vulnerability allows an attacker to store an HTML
file in an area that is not protected by the policies of the "Internet
Zone." This file may then be used to open arbitrary files on the
victim's machine and send their contents back to the attacker.
In addition, the "Cache Bypass" vulnerability could be used in
conjunction with other vulnerabilities to allow an intruder to execute
arbitrary code on the victim's machine.
III. Solution
Microsoft has released Microsoft Security Bulletin MS00-046, which
points to a patch for this vulnerability. We strongly encourage you to
read this bulletin and apply the patch. MS00-046 is available at
http://www.microsoft.com/technet/security/bulletin/MS00-046.asp
_________________________________________________________________
The CERT Coordination Center would like to thank Microsoft for its
assistance in developing this advisory.
_________________________________________________________________
Author: Jeffrey P. Lanza
______________________________________________________________________
This document is available from:
http://www.cert.org/advisories/CA-2000-14.html
______________________________________________________________________
CERT/CC Contact Information
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
U.S.A.
CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4)
Monday through Friday; they are on call for emergencies during other
hours, on U.S. holidays, and on weekends.
Using encryption
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Our public PGP key is available from
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If you prefer to use DES, please call the CERT hotline for more
information.
Getting security information
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Patent and Trademark Office.
______________________________________________________________________
NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed or
implied as to any matter including, but not limited to, warranty of
fitness for a particular purpose or merchantability, exclusivity or
results obtained from use of the material. Carnegie Mellon University
does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
_________________________________________________________________
Conditions for use, disclaimers, and sponsorship information
Copyright 2000 Carnegie Mellon University
Revision History
July 26, 2000: Initial release
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