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Two IE Bulletins Cure a Dozen Security Flaws

Corey Nachreiner

Severity: High

14 June, 2011

Summary:

Exposure:

In two security bulletins [ MS11-050 / MS11-052 ] released today as part of Patch Day, Microsoft describes twelve privately reported vulnerabilities in Internet Explorer (IE) 9.0 and earlier versions, running on all current versions of Windows. They rate both of these bulletins as Critical.

Microsoft warns of 11 new IE vulnerabilities in their cumulative IE update. Though these 11 flaws differ technically, most of them (eight) share the same general scope and impact. They all involve memory corruption issues having to do with how IE handles various HTML elements, such as link properties and layout memory. If an attacker can lure one of your users to a web page containing malicious web code, he could exploit any one of these memory corruption vulnerabilities to execute code on that user’s computer, inheriting that user’s privileges. Typically, Windows users have local administrative privileges, in which case the attacker gains complete control of the victim’s computer. Attackers often leverage these type of code execution vulnerabilities to launch Drive-by Download attacks.

The remaining  issues cover less severe  information disclosure vulnerabilities.

If you’d like to know more about the technical differences between these flaws, see the “Vulnerability Information” section of Microsoft’s bulletin. Technical differences aside, the memory corruption flaws in IE pose significant risk. You should download and install the IE cumulative patch immediately.

IE also suffers from a memory corruption vulnerability having to do with how it parses specially crafted Vector Markup Language (VML) that references uninitialized or deleted objects. By enticing one of your users to a specially crafted web page, an attacker could leverage this flaw to execute code on that user’s computer, with their privileges. As usual, if the victim has local administrative privilege, the attacker gains complete control of the victim’s computer. This flaw is similar in scope to previous VML IE flaws, like the one we demonstrate in this old Wire video.

Keep in mind, today’s attackers commonly hijack legitimate web pages and booby-trap them with malicious code. Typically, they do this via hosted web ads or through SQL injection and XSS attacks. Even recognizable and authentic websites could pose a risk to your users if hijacked in this way.

Solution Path:

These patches fix serious issues. You should download, test, and deploy the appropriate IE patches immediately, or let Windows Automatic Update do it for you.

MS11-050:

* Note: These flaws do not affect Windows Server 2008 administrators who installed using the Server Core installation option.

MS11-052:

* Note: These flaws do not affect Windows Server 2008 administrators who installed using the Server Core installation option.

For All WatchGuard Users:

These types of attacks typically look like normal-looking HTTP traffic, which you must allow if your network users need to access the World Wide Web. Therefore, the patches above are your best solution.

Status:

Microsoft has released patches to fix these vulnerabilities.

References:

This alert was researched and written by Corey Nachreiner, CISSP.

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