CERT Advisory CA-2001-36 Microsoft Internet Explorer Does Not Respect Content-Disposition and Content-Type MIME HeadersFrom: CERT Advisory (email@example.com)
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Date: Wed, 19 Dec 2001 17:59:33 -0500 (EST) From: CERT Advisory <firstname.lastname@example.org> To: email@example.com
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CERT Advisory CA-2001-36 Microsoft Internet Explorer Does Not Respect
Content-Disposition and Content-Type MIME Headers
Original release date: December 19, 2001
Last revised: --
A complete revision history can be found at the end of this file.
* Microsoft Internet Explorer 6.0 for Windows
* Microsoft Outlook, Outlook Express, or any other software that
utilizes vulnerable versions of Internet Explorer to render HTML
Microsoft Internet Explorer contains a vulnerability in its handling of
certain MIME headers in web pages and HTML email messages. This
vulnerability may allow an attacker to execute arbitrary code on the
victim's system when the victim visits a web page or views an HTML
Web pages and HTML email messages usually contain HTML text, but other
files may also be included. The MIME headers Content-Disposition and
Content-Type provide the information needed by the HTML rendering
software to determine the type of these files. In Microsoft Internet
Explorer, these MIME headers are consulted when evaluating whether to
process an embedded file, but they are ignored when the file is
For example, if an executable (.exe) file is embedded with MIME headers
that misrepresent it as a JPEG image file (.jpg), Internet Explorer
will treat the file as a JPEG when evaluating whether it is safe to
open. Once this evaluation is complete, the file will be opened
according to its .exe file extension and will be executed on the local
This behavior results in a vulnerability that allows attackers to
bypass the security measures that typically screen out executable code.
This code would be executed with the privileges the user who views the
web page or email message.
Users who view a malicious web site or HTML email message may be able
to prevent the execution of the attacker's code by using the download
progress dialog box to cancel the download. However, depending on the
size of the embedded file and the speed of the network connection,
users may not have time to cancel the file download.
The CERT/CC is tracking this vulnerability as VU#443699, which
corresponds directly to the "File Execution" vulnerability described in
Microsoft Security Bulletin MS01-058. This Microsoft bulletin is
This vulnerability is being referenced in CVE as CAN-2001-0727.
By convincing a user to view a malicious web page or HTML email
message, a remote attacker can cause the user to execute arbitrary
code. Any such code would run with the privileges of the user who
attempted to view the content.
Apply a patch from your vendor
Microsoft has released a cumulative patch for Internet Explorer that
corrects this vulnerability and several others. For more information
about the patch and the vulnerabilities, please see Microsoft
Security Bulletin MS01-058:
Disable file downloads in all security zones
As a workaround, you can prevent malicious files from being
downloaded by disabling file downloads in all security zones. Note
that this decision will impact browser functionality.
Appendix A. - Vendor Information
This appendix contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we will
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their
The following documents regarding this vulnerability are available
The CERT Coordination Center acknowledges Jouko Pynnonen as the
discoverer of this vulnerability and thanks Microsoft for the
information presented in MS01-058.
Author: This document was written by Jeffrey P. Lanza.
This document is available from:
CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
CERT/CC personnel answer the hotline 08:00-17:00 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.
We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
If you prefer to use DES, please call the CERT hotline for more
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Patent and Trademark Office.
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Conditions for use, disclaimers, and sponsorship information
Copyright 2001 Carnegie Mellon University.
December 19, 2001: Initial release
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