May's IE Update Corrects Two New Memory Corruptions

Summary:

• This vulnerability affects: All current versions of Internet Explorer
• How an attacker exploits it: By enticing one of your users to visit a web page containing malicious content
• Impact: Various, in the worst case an attacker can execute code on your user’s computer, potentially gaining complete control of it
• What to do: Deploy the appropriate Internet Explorer patches immediately, or let Windows Automatic Update do it for you

Exposure:

In a security bulletin released today as part of Patch Day, Microsoft describes two new vulnerabilities that affect all current versions of Internet Explorer (IE). Microsoft rates the aggregate severity of these new flaws as Critical.

Though the two vulnerabilities differ technically, they share the same general scope and impact, and involve memory corruption flaws having to do with how IE handles certain HTML objects. If an attacker can lure one of your users to a web page containing malicious web code, he could exploit either 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 that case, the attacker could exploit these flaws to gain complete control of the victim’s computer.

Technical differences aside, the memory corruption flaws in IE pose significant risk. You should download and install the IE cumulative patch immediately. Also note, this IE cumulative patch also includes a fix for the zero day IE flaw Microsoft fixed earlier, in an out-of-cycle update. If, for some reason, you haven’t applied that update yet, this is a good time to fix that serious zero day flaw.

Keep in mind, today’s attackers often hijack legitimate web pages and booby-trap them with malicious code. Typically, they do this via hosted web ads or through SQL injection and cross-site scripting (XSS) attacks. Even recognizable and authentic websites could pose a risk to your users if hijacked in this way, and the vulnerabilities described in today’s bulletin are perfect for use in drive-by download attacks.

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 April IE security bulletin.

For All WatchGuard Users:

Good News! 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 the memory corruption vulnerabilities described in Microsoft’s alert:

• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2014-0310)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2014-1815)

Your XTM appliance should get this new IPS 4.414 signature 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:

• MS Security Bulletin MS14-029

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

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