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Two Critical IE Bulletins Fix Zero Day Vulnerability and More

Corey Nachreiner

Severity: High

Summary:

Exposure:

As part of today’s Patch Day, Microsoft released two security bulletins (MS13-037/MS13-038) describing a dozen new security vulnerabilities that affect all current versions of Internet Explorer (IE). They rate both updates as Critical.

Over the last few months, most of the new flaws affecting IE are what developers call “use after free” vulnerabilities – a type of memory corruption flaw that attackers can leverage to execute arbitrary code. May’s duo of IE bulletins continues this theme, with all but one of the vulnerabilities falling under this class of flaw.

Though these dozen vulnerabilities differ technically, they share the same general scope and impact (with one small exception). If an attacker can lure one of your users to a web page containing maliciously crafted HTML, he could exploit any of these 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 can exploit these flaws to gain complete control of the victim’s computer. Keep in mind, attackers often hijack legitimate web pages and booby trap them with this sort of malicious code, in what the industry refers to as a “watering hole” attack.

Typically, Microsoft only releases one IE cumulative update a month. However, over the last few weeks attackers have exploited a zero day IE8 vulnerability in the wild—most notably against the Department of Labor (DoL) web site. We talked about this exploit in last week’s security video. Although Microsoft had released a temporary “FixIt” to mitigate this serious vulnerability, today’s second IE bulletin (MS13-038) rectifies the issue more completely. Attackers are still exploiting this flaw in the wild. They’ve worked it into their underground exploit toolkits, and even the popular Metasploit framework contains a public version of the exploit. We highly recommend you install both of Microsoft’s IE updates immediately (after testing, of course).

If you’d like more technical detail about any of these flaws, see the “Vulnerability Information” section in both of Microsoft’s bulletins (MS13-037/MS13-038).

Solution Path:

You should download, test, and deploy the appropriate IE updates immediately, or let Windows Automatic Update do it for you. You can find links to the various IE updates in the “Affected and Non-Affected Software” section of Microsoft’s IE security bulletins:

For All WatchGuard Users:

WatchGuard’s Gateway Antivirus and Intrusion Prevention services can often prevent these sorts of attacks, or the malware they try to distribute. For instance, our IPS signature team has developed signatures that can detect and block many of the “use after free” vulnerabilities described in Microsoft’s alert:

Your XTM appliance should get this new IPS update shortly.

Furthermore, our Reputation Enabled Defense (RED) and WebBlocker services can often prevent your users from accidentally visiting malicious (or legitimate but booby-trapped) web sites that contain these sorts of attacks. Nonetheless, we still recommend you install Microsoft’s updates to completely protect yourself from all of these flaws.

Status:

Microsoft has released patches to fix these vulnerabilities.

References:

This alert was researched and written by Corey Nachreiner, CISSP (@SecAdept).

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