February 26th, 2002, 03:30 PM
CERT Advisory CA-2002-04 Buffer Overflow in Microsoft Internet Explorer
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CERT Advisory CA-2002-04 Buffer Overflow in Microsoft Internet Explorer
Original release date: February 25, 2002
Last revised: --
A complete revision history can be found at the end of this file.
* Microsoft Internet Explorer
* Microsoft Outlook and Outlook Express
* Other applications that use the Internet Explorer HTML rendering
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
Internet Explorer supports the 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:
Internet Explorer uses attributes of the 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
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.
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.
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
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
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
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:
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
* Outlook 98
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
Microsoft has released a Security Bulletin and a Knowledge Base
Article addressing this vulnerability:
* Security Bulletin MS02-005
* Knowledge Base Article Q317731
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
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:
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February 25, 2002: Initial release
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February 26th, 2002, 08:27 PM
more of these every day. Since the US govt got nowhere with them maybe the Euro commission will. Msoft I mean.
February 26th, 2002, 08:38 PM
The microsoft post (below) was posted February 11. This is the 25th. This just goes to show how slow CERT has become. Yet CERT used to be the First place that administrators went to find out about patches. Now, your system should be patched before you get the message from CERT.
\"Ignorance is bliss....
but only for your enemy\"
February 26th, 2002, 08:43 PM
yeah I used to go to cert everyday but now it has slipped...
March 3rd, 2002, 05:02 PM
heh and thats just the number of the vunerability found that day for a micro$oft product
The CERT/CC is tracking this vulnerability as VU#932283