Microsoft Internet Explorer CSS style element vulnerability

Overview

Microsoft Internet Explorer (IE) does not safely reference CSS style elements. Using a specially crafted HTML page, an attacker can cause IE to crash and potentially execute arbitrary code.

Description

IE contains a vulnerability in the way it references CSS style elements. Processing a specially crafted HTML page could cause IE to access an invalid memory location and crash. Using heap-spraying techniques, an attacker could leverage the crash to execute arbitrary code.

Please see Microsoft Security Advisory (977981).

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Impact

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message), an attacker could execute arbitrary code with the privileges of the user.

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Solution

A complete solution is not available.

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Disable Active scripting

As noted in Microsoft Security Advisory (977981), consider disabling Active Scripting. Instructions for disabling Active scripting can be found in Microsoft Security Advisory (977981 and "Securing Your Web Browser."

Enable DEP

As noted in Microsoft Security Advisory (977981), consider enabling Data Execution Prevention (DEP).

Disabling scripting and enabling DEP do not resolve the vulnerability, but they greatly lower the chances of an attacker being able to execute arbitrary code.

Use Internet Explorer 8

According to Microsoft Security Advisory (977981), Internet Explorer 8 is not affected.

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Vendor Information

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Microsoft Corporation __ Affected

Notified: November 23, 2009 Updated: November 24, 2009

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

Please see Microsoft Security Advisory (977981).

Vendor References

• <http://www.microsoft.com/technet/security/advisory/977981.mspx&gt;

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.microsoft.com/technet/security/advisory/977981.mspx&gt;
• <http://www.securityfocus.com/archive/1/507984/30/0/threaded&gt;
• <http://www.symantec.com/connect/blogs/zero-day-internet-explorer-exploit-published&gt;
• <http://www.computerworld.com/s/article/9141278/New_attack_fells_Internet_Explorer&gt;
• <http://seclists.org/bugtraq/2009/Nov/148&gt;
• <http://blogs.msdn.com/ie/archive/2008/04/08/ie8-security-part-I_3A00_-dep-nx-memory-protection.aspx&gt;

Acknowledgements

This vulnerability was publicly disclosed by [email protected] and/or [email protected].

This document was written by Art Manion.

Other Information

CVE IDs:	CVE-2009-3672
Severity Metric:	29.25 Date Public: