MS03-023: Buffer Overrun In HTML Converter

[Steven]

-----BEGIN PGP SIGNED MESSAGE-----

- - ---------------------------------------------------------------

Title: Buffer Overrun In HTML Converter Could Allow Code

Execution (823559)

Date: 09 July 2003

Software: Microsoft® Windows ® 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/...in/MS03-023.asp

http://www.microsoft.com/security/security...ns/ms03-023.asp

- - ---------------------------------------------------------------

Issue:

======

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.

Mitigating factors:

====================

- 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.

Risk Rating:

============

Critical

Patch Availability:

===================

- A patch is available to fix this vulnerability. Please read

the Security Bulletins at

http://www.microsoft.com/technet/security/...in/ms03-023.asp

http://www.microsoft.com/security/security...ns/ms03-023.asp

for information on obtaining this patch.

- - ---------------------------------------------------------------

Edited July 9, 2003 by xStainDx