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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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