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CERT® Advisory CA-2003-14 Buffer Overflow in Microsoft Windows HTML Conversion LibraryOriginal issue date: July 14, 2003Last revised: -- Source: CERT/CC A complete revision history is at the end of this file. Systems Affected
OverviewA buffer 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. I. DescriptionMicrosoft 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." The 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 the 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 the 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. This vulnerability 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. Further information is available in VU#823260. Common Vulnerabilities and Exposures (CVE) refers to this issue as CAN-2003-0469. II. ImpactAn attacker 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. III. SolutionApply a patchApply the appropriate patch as specified by Microsoft Security Bulletin MS03-023. Modify Internet Explorer security zone configurationModify 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:
Note that disabling Active scripting provides defense against other attacks that are outside the scope of this document. Instructions 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 InformationThis appendix 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. Microsoft
Appendix B. References
This vulnerability was publicly reported by Digital Scream. Feedback can be directed to the author, Art Manion. This document is available from: http://www.cert.org/advisories/CA-2003-14.html CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: 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. Using encryptionWe 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 information. Getting security informationCERT publications and other security information are available from our web site * "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.
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Copyright 2003 Carnegie Mellon University. Revision History July 14, 2003: Initial release |
