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CERT Advisory
CA-2002-04 Buffer Overflow in Microsoft Internet Explorer
Original
release date: February 25, 2002
Last revised: --
Source: CERT/CC
A complete
revision history can be found at the end of this file.
Systems
Affected
* Microsoft
Internet Explorer
* Microsoft Outlook and Outlook Express
* Other applications that use the Internet Explorer HTML rendering
engine
Overview
Microsoft
Internet Explorer contains a buffer overflow vulnerability
in its handling of embedded objects in HTML documents. This
vulnerability could allow an attacker to execute arbitrary code on the
victim's system when the victim visits a web page or views an HTML
email message.
I. Description
Internet
Explorer supports the <EMBED> directive, which can be used to
include arbitrary objects in HTML documents. Common types of embedded
objects include multimedia files, Java applets, and ActiveX controls.
The SRC attribute specifies the source path and filename of an object.
For example, a MIDI sound might be embedded in a web page with the
following HTML code:
<EMBED
TYPE="audio/midi" SRC="/path/sound.mid" AUTOSTART="true">
Internet
Explorer uses attributes of the <EMBED> directive and MIME
information from the web server to determine how to handle an embedded
object. In most cases, a separate application or plugin is used.
A group
of Russian researchers, SECURITY.NNOV, has reported that
Internet Explorer does not properly handle the SRC attribute of the
<EMBED> directive. An HTML document, such as a web page or HTML
email
message, that contains a crafted SRC attribute can trigger a buffer
overflow, executing code with the privileges of the user viewing the
document. Microsoft Internet Explorer, Outlook, and Outlook Express
are vulnerable. Other applications that use the Internet Explorer HTML
rendering engine, such as Windows compiled HTML help (.chm) files and
third-party email clients, may also be vulnerable.
The CERT/CC
is tracking this vulnerability as VU#932283, which
corresponds directly to the "buffer overrun" vulnerability
described
in Microsoft Security Bulletin MS02-005.
This vulnerability
has been assigned the CVE identifier CAN-2002-0022.
II. Impact
By convincing
a user to view a malicious HTML document, an attacker
can cause the Internet Explorer HTML rendering engine to execute
arbitrary code with the privileges of the user who viewed the HTML
document. This vulnerability could be exploited to distribute viruses,
worms, or other malicious code.
III. Solution
Apply a
patch
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 MS02-005:
http://www.microsoft.com/technet/security/bulletin/MS02-005.asp
Disable
ActiveX Controls and Plugins
In Internet
Explorer, plugins may be used to view, play, or otherwise
process embedded objects. The execution of embedded objects is
controlled by the "Run ActiveX Controls and Plugins" security
option.
Disabling this option will prevent embedded objects from being
processed, and will therefore prevent exploitation of this
vulnerability.
According
to MS02-005:
The vulnerability
could not be exploited if the "Run ActiveX
Controls and Plugins" security option were disabled in the Security
Zone in which the page was rendered. This is the default condition
in the Restricted Sites Zone, and can be disabled manually in any
other Zone.
At a minimum,
disable the "Run ActiveX Controls and Plugins" security
option in the Internet Zone and the zone used by Outlook or Outlook
Express. The "Run ActiveX Controls and Plugins" security option
is
disabled in the "High" zone security setting. Instructions
for
configuring the Internet Zone to use the "High" zone security
setting
can be found in the CERT/CC Malicious Web Scripts FAQ:
http://www.cert.org/tech_tips/malicious_code_FAQ.html#steps
Apply the
Outlook Email Security Update
Another
way to effectively disable the processing of ActiveX controls
and plugins in Outlook is to install the Outlook Email Security
Update. The update configures Outlook to open email messages in the
Restricted Sites Zone, where the "Run ActiveX Controls and Plugins"
security option is disabled by default. In addition, the update
provides further protection against malicious code that attempts to
propagate via Outlook.
* Outlook
2002 and Outlook Express 6
The functionality of the Outlook Email Security Update is included
in Outlook 2002 and Outlook Express 6.
* Outlook 2000
http://office.microsoft.com/downloads/2000/Out2ksec.aspx
* Outlook 98
http://office.microsoft.com/downloads/9798/Out98sec.aspx
Appendix A. - Vendor Information
This appendix
contains information provided by vendors for this
advisory. When vendors report new information to the CERT/CC, we
update this section and note the changes in our revision history. If
a
particular vendor is not listed below, we have not received their
comments.
Microsoft
Microsoft
has released a Security Bulletin and a Knowledge Base
Article addressing this vulnerability:
* Security Bulletin MS02-005
http://www.microsoft.com/technet/security/bulletin/MS02-005.asp
* Knowledge Base Article Q317731
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q317731
Cyrusoft
Our email
client Mulberry does not use the core HTML rendering engine
library for its HTML display, and so is not affected by the bug in
that library. Having looked at the details of this alert I can also
confirm that our own HTML rendering engine is not affected by this,
as
it ignores the relevant tags.
Appendix B. - References
1. http://www.kb.cert.org/vuls/id/932283
2. http://www.security.nnov.ru/advisories/mshtml.asp
3. http://www.microsoft.com/technet/security/bulletin/MS02-005.asp
4. http://support.microsoft.com/default.aspx?scid=kb;en-us;Q317731
5. http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0022
6. http://msdn.microsoft.com/workshop/author/dhtml/reference/objects/
embed.asp
7. http://developer.netscape.com/docs/manuals/htmlguid/tags14.htm#128
6379
_________________________________________________________________
The CERT/CC
thanks ERRor and DarkZorro of domain Hell and 3APA3A of
SECURITY.NNOV for reporting this issue to us.
_________________________________________________________________
Author:
Art Manion
______________________________________________________________________
This document
is available from:
http://www.cert.org/advisories/CA-2002-04.html
______________________________________________________________________
CERT/CC
Contact Information
Email:
cert@cert.org
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/CC
personnel answer the hotline 08:00-17:00 EST(GMT-5) /
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Using encryption
We strongly
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Our public PGP key is available from
http://www.cert.org/CERT_PGP.key
If you
prefer to use DES, please call the CERT hotline for more
information.
Getting
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______________________________________________________________________
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Any material furnished by Carnegie Mellon University and the Software
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_________________________________________________________________
Conditions
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Copyright
2002 Carnegie Mellon University.
Revision
History
February 25, 2002: Initial release
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