[Am-info] CERT Advisory CA-2002-04 Buffer Overflow in Microsoft Internet Explorer
Fred A. Miller
fm@cupserv.org
Tue, 26 Feb 2002 13:25:57 -0500
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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.
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/
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Using encryption
We strongly urge you to encrypt sensitive information sent by
email.
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.
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- --
Fred A. Miller
Systems Administrator
Cornell Univ. Press Services
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