Microsoft Security Bulletin (MS00-055)

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Microsoft Security Bulletin (MS00-055)
- --------------------------------------

Patch Available for "Scriptlet Rendering" Vulnerability

Originally Posted: August 09, 2000

Summary
=======
Microsoft has released a patch that eliminates two security
vulnerabilities in Microsoft(r) Internet Explorer. The
vulnerabilities could allow a malicious web site operator to read -
but not add, change, or delete - files on the computer of a visiting
user.

As discussed in the Patch Availability section below, this patch also
provides protection against several security vulnerabilities that
have been discussed in previous security bulletins. We have delivered
a comprehensive patch in order to minimize the number of patches
customers need to apply.

Frequently asked questions regarding this vulnerability
and the patch can be found at
http://www.microsoft.com/technet/security/bulletin/fq00-055.asp

Issue
=====
There are two vulnerabilities at issue here:
 - The "Scriptlet Rendering" vulnerability. The ActiveX
   control that is used to invoked scriptlets is essentially
   a rendering engine for HTML. However, it will render any
   file type, rather than rendering HTML files only. This
   opens the door to a scenario in which a malicious web
   site operator could provide bogus information consisting
   of script, solely for the purpose of introducing it into
   an IE system file with a known name, then use the
   Scriptlet control to render the file. The net effect
   would be to make the script run in the Local Computer
   Zone, at which point it could access files on the user's
   local file system.
 - A new variant of the "Frame Domain Verification"
   vulnerability. As discussed in Microsoft Security Bulletin
   MS00-033, two functions do not enforce proper separation
   of frames in the same window that reside in different
   domains. The new variant involves an additional function
   with the same flaw. The net effect of the vulnerability
   would be to enable a malicious web site operator to open
   two frames, one in his domain and another on the user's
   local file system, and enable the latter to pass information
   to the former.

In order to exploit either vulnerability, a malicious web site
operator would need to know or guess the exact name and path of each
file he wanted to view. Even then, he could only view file types that
can be opened in a browser window - for instance, .txt or .doc files,
but not .exe or .dat files. If the web site were in a Zone in which
Active Scripting were disabled, neither vulnerability could be
exploited.

Affected Software Versions
==========================
 - Microsoft Internet Explorer 4.x
 - Microsoft Internet Explorer 5.x

Patch Availability
==================
 - http://www.microsoft.com/windows/ie/download/critical/patch11.htm

Note: In addition to eliminating the two vulnerabilities discussed
above, this patch also protects against several previously-discussed
vulnerabilities. Customers who apply this patch will also be
protected against the vulnerabilities discussed in the following
Security Bulletins:
 - Microsoft Security Bulletin MS00-033
 - Microsoft Security Bulletin MS00-039
 - Microsoft Security Bulletin MS00-049
In addition, for IE 5.5 systems only, this patch also eliminates the
vulnerability discussed in Microsoft Security Bulletin MS00-042.

Note: Customers who install this patch on versions other than IE
5.01, IE 5.01 SP1, or IE 5.5 may receive a message reading "This
update does not need to be installed on this system". This message is
incorrect. More information is available in KB article Q266336.

Note: Additional security patches are available at the Microsoft
Download Center

More Information
================
Please see the following references for more information related to
this issue.
 - Frequently Asked Questions: Microsoft Security Bulletin MS00-055,
   http://www.microsoft.com/technet/security/bulletin/fq00-055.asp
 - Microsoft Knowledge Base article Q266336 discusses this issue
   and will be available soon.
 - Microsoft Security Bulletin MS00-033,
   Patch Available for "Frame Domain Verification", "Unauthorized
   Cookie Access", and "Malformed Component Attribute"
   Vulnerabilities,
   http://www.microsoft.com/technet/security/bulletin/ms00-033.asp
 - Microsoft Security Bulletin MS00-039,
   Patch Available for "SSL Certificate Validation" Vulnerabilities,
   http://www.microsoft.com/technet/security/bulletin/ms00-039.asp
 - Microsoft Security Bulletin MS00-042,
   Patch Available for "Active Setup Download" Vulnerability,
   http://www.microsoft.com/technet/security/bulletin/ms00-042.asp
 - Microsoft Security Bulletin MS00-049,
   Patches Available for "Office HTML" and "IE Script" Security
   Vulnerabilities,
   http://www.microsoft.com/technet/security/bulletin/ms00-049.asp
 - Microsoft TechNet Security web site,
   http://www.microsoft.com/technet/security/default.asp

Obtaining Support on this Issue
===============================
This is a fully supported patch. Information on contacting Microsoft
Product Support Services is available at
http://support.microsoft.com/support/contact/default.asp.

Acknowledgments
===============
Microsoft thanks  Juan Carlos Garcia Cuartango of Spain
(www.kriptopolis.com) for reporting the "Scriptlet Rendering" issue
to us and working with us to protect customers.

Revisions
=========
 - August 09, 2000: Bulletin Created.

- ---------------------------------------------------------------

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.

Last Updated August 09, 2000


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