Microsoft Internet Explorer VML Buffer Overflow

Systems Affected

* Microsoft Windows

* Microsoft Internet Explorer

Overview

Microsoft Internet Explorer (IE) fails to properly handle Vector
Markup Language (VML) tags. This creates a buffer overflow
vulnerability that could allow a remote attacker to execute
arbitrary
code.

I. Description

Microsoft Internet Explorer contains a stack buffer overflow in code
that handles VML. More information is available in Vulnerability
Note
VU#416092, Microsoft Security Advisory (925568), and Microsoft
Security Bulletin MS06-055.

Note that this vulnerability is being exploited.

II. Impact

By convincing a user to open a specially crafted HTML document, such
as a web page or HTML email message, a remote attacker could execute
arbitrary code with the privileges of the user running IE.

III. Solution

Apply update from Microsoft

Microsoft has provided an update to correct this vulnerability in
Microsoft Security Bulletin MS06-055.

This update is available on the Microsoft Update site.

System administrators may wish to consider using Windows Server
Update
Services (WSUS).

Disable VML support

Microsoft Security Advisory (925568) suggests the following
techniques
to disable VML support:

* Un-register Vgx.dll on Windows XP Service Pack 1; Windows XP
Service Pack 2; Windows Server 2003 and Windows Server 2003
Service Pack 1

* Modify the Access Control List on Vgx.dll to be more restrictive

* Configure Internet Explorer 6 for Microsoft Windows XP Service

Pack 2 to disable Binary and Script Behaviors in the Internet
and
Local Intranet security zone

Disabling VML support may cause web sites and applications that use
VML to function improperly.

Render email as plain text

Microsoft Security Advisory (925568) suggests configuring Microsoft
Outlook and Outlook Express to render email messages in plain text
format.

Do not follow unsolicited links

In order to convince users to visit their sites, attackers often use
URL encoding, IP address variations, long URLs, intentional
misspellings, and other techniques to create misleading links.

Do
not
click on unsolicited links received in email, instant messages, web
forums, or internet relay chat (IRC) channels. Type URLs directly
into
the browser to avoid these misleading links. While these are
generally
good security practices, following these behaviors will not prevent
exploitation of this vulnerability in all cases, particularly if a
trusted site has been compromised or allows cross-site scripting.