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CA-2003-14 Buffer Overflow in Microsoft Windows HTML
issue date: July 14, 2003
Last revised: --
revision history is at the end of this file.
98 and 98 Second Edition (SE)
* Windows NT 4.0 and 4.0 Terminal Server Edition (TSE)
* Windows Millennium Edition (Me)
* Windows 2000
* Windows XP
* Windows Server 2003
overflow vulnerability exists in a shared HTML conversion
library included in Microsoft Windows. An attacker could exploit this
vulnerability to execute arbitrary code or cause a denial of service.
Windows includes a shared HTML conversion library
(html32.cnv). According to Microsoft Security Bulletin MS03-023, "The
HTML converter is an extension which allows applications to convert
HTML data into Rich Text Format (RTF) while maintaining the formatting
and structure of the data as well as the text. The converter also
supports the conversion of RTF data into HTML."
conversion library contains a buffer overflow vulnerability
that can be triggered by a specially crafted align attribute in an
<HR> element. The library can be loaded by any application on
system. For example, Internet Explorer (IE) uses the library to handle
HTML data stored in the clipboard. Using script, an attacker can cause
IE to copy a crafted <HR> element into the clipboard and load
library. The attacker could accomplish this by convincing a victim to
view an HTML web page or HTML email message with IE, Outlook, or
Outlook Express in a zone where Active scripting and Allow paste
operations via script are enabled.
is not limited to IE, Outlook, or Outlook Express.
Any program, including non-Microsoft applications, can use the
vulnerable library and may present other vectors of attack.
information is available in VU#823260. Common Vulnerabilities
and Exposures (CVE) refers to this issue as CAN-2003-0469.
could execute arbitrary code with the privileges of the
process that loaded the HTML conversion library. The attacker could
also crash the process, causing a denial of service.
the appropriate patch as specified by Microsoft Security
Internet Explorer security zone configuration
one or both of the following IE security zone settings in the
Internet zone and the zone(s) used by Outlook, Outlook Express, and
any other application that uses Internet Explorer or the WebBrowser
ActiveX control to render HTML:
Allow paste operations via script to Disable
Active scripting to Disable
of these changes will prevent attacks that depend on scripting
in the IE HTML rendering engine. However, these changes are not
complete solutions, and they do not prevent attacks that use other
disabling Active scripting provides defense against other
attacks that are outside the scope of this document.
for modifying IE 5 security zone settings can be found in
the CERT/CC Malicious Web Scripts FAQ. In IE 6, the High security zone
setting includes both of these changes.
Appendix A. Vendor Information
contains information provided by vendors. When vendors
report new information, this section is updated and the changes are
noted in the revision history. If a vendor is not listed below, we
have not received their comments.
see Microsoft Security Bulletin MS03-023.
Appendix B. References
Vulnerability Note VU#823260 -
* Microsoft Security Bulletin MS03-023 -
was publicly reported by Digital Scream.
can be directed to the author, Art Manion.
is available from:
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Fax: +1 412-268-6989
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2003: Initial release
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