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Title: Buffer Overrun In HTML Converter Could Allow Code
Date: 09 July 2003
Software: Microsoft(r) Windows (r) 98
Microsoft Windows 98 Second Edition
Microsoft Windows Me
Microsoft Windows NT 4.0
Microsoft Windows NT 4.0 Terminal Services Edition
Microsoft Windows 2000
Microsoft Windows XP
Microsoft Windows Server 2003
Impact: Allow an attacker to execute code of their choice Max Risk: Critical Bulletin: MS03-023
Microsoft encourages customers to review the Security Bulletins at: http://www.microsoft.com/technet/security/bulletin/MS03-023.asp http://www.microsoft.com/security/security_bulletins/ms03-023.asp
All versions of Microsoft Windows contain support for file conversion within the operating system. This functionality allows users of Microsoft Windows to convert file formats from one to another. In particular, Microsoft Windows contains support for HTML conversion within the operating system. This functionality allows users to view, import, or save files as HTML.
There is a flaw in the way the HTML converter for Microsoft Windows handles a conversion request during a cut-and-paste operation. This flaw causes a security vulnerability to exist. A specially crafted request to the HTML converter could cause the converter to fail in such a way that it could execute code in the context of the currently logged-in user. Because this functionality is used by Internet Explorer, an attacker could craft a specially formed Web page or HTML e-mail that would cause the HTML converter to run arbitrary code on a user's system. A user visiting an attacker's Web site could allow the attacker to exploit the vulnerability without any other user action.
To exploit this vulnerability, the attacker would have to create a specially-formed HTML e-mail and send it to the user. Alternatively, an attacker would have to host a malicious Web site that contains a Web page designed to exploit this vulnerability. The attacker would then have to persuade a user to visit that site.
By default, Internet Explorer on Windows Server 2003 runs in Enhanced Security Configuration. This default configuration of Internet Explorer blocks automatic exploitation of this attack. If Internet Explorer Enhanced Security Configuration has been disabled, the protections put in place that prevent this vulnerability from being automatically exploited would be removed.
In the Web-based attack scenario, the attacker would have to host a Web site that contained a Web page used to exploit this vulnerability. An attacker would have no way to force users to visit a malicious Web site outside the HTML e-mail vector. Instead, the attacker would need to lure them there, typically by getting them to click a link that would take them to the attacker's site.
Exploiting the vulnerability would allow the attacker only the same privileges as the user. Users whose accounts are configured to have few privileges on the system would be at less risk than ones who operate with administrative privileges.
for information on obtaining this patch.
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