Microsoft Internet Explorer fails to properly handle chained Cascading Style Sheets

Overview

Microsoft Internet Explorer fails to properly handle chained Cascading Style Sheets (CSS). This can allow a remote attacker to execute arbitrary code on a vulnerable system.

Description

CSS is a mechanism for adding style to web documents. Microsoft Internet Explorer contains a vulnerability in the handling of chained CSS. An attacker can exploit this vulnerability by creating a specially crafted HTML document that causes memory corruption when it is viewed with Internet Explorer.

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Impact

By convincing a user to view a specially crafted HTML document (e.g., a web page, an HTML email message, or an email attachment), an attacker could execute arbitrary code with the privileges of the user. The attacker could also cause Internet Explorer (or the program using the WebOC control) to crash.

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Solution

Apply an update

This vulnerability is addressed in Microsoft Security Bulletin MS06-042.

Note that this patch may cause problems for certain users. Per Microsoft Knowledgebase Article 923762:
_Consider the following scenario. You run Microsoft Internet Explorer 6 Service Pack 1 (SP1) on a computer that is running Microsoft Windows XP with Service Pack (SP1) or Microsoft Windows 2000 with Service Pack 4 (SP4). You install the Internet Explorer cumulative security update that is documented in Microsoft Knowledge Base article 918899. In this scenario, Internet Explorer unexpectedly exits when you view a Web site that uses the HTTP 1.1 protocol and compression. _

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Disable Active Scripting

This vulnerability can be mitigated by disabling Active Scripting, as specified in the “Securing Your Web Browser” document. Although this does not remove the vulnerability, it does block known attack vectors.

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Vendor Information

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Updated: August 08, 2006

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

Please see Microsoft Security Bulletin MS06-042.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23262004 Feedback>).

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.microsoft.com/technet/security/bulletin/ms06-042.mspx&gt;
• <http://www.us-cert.gov/reading_room/securing_browser/#Internet_Explorer&gt;
• <http://www.w3.org/Style/CSS/&gt;
• <http://secunia.com/advisories/21396/&gt;

Acknowledgements

This vulnerability was reported by Microsoft, who in turn credit Sam Thomas.

This document was written by Will Dormann.

Other Information

CVE IDs:	CVE-2006-3451
Severity Metric:	20.25 Date Public: