In a security bulletin released as part of Patch Day, Microsoft posted an update that fixes a 37 new vulnerabilities in all current versions of Internet Explorer (IE). Microsoft rates the aggregate severity of these new flaws as Critical.
All but one of the vulnerabilities described in this alert are memory corruption vulnerabilities, which share the same general scope and impact. If an attacker can lure you to a web page containing malicious web code, he can exploit these flaws to execute code on your computer, inheriting your privileges. If you have local administrative privileges, which most Windows users do, the attack could potentially gain full control of your computer.
These types of memory corruption vulnerabilities are ideal for attackers launching drive-by download attacks—a class of attack where malicious code hidden on a web page can silently install malware on your computer. 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. In fact, one of today’s fixes closes a zero day vulnerability that attackers have exploited in the wild. I highly recommend you install this update immediately
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.
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 some of the memory corruption vulnerabilities described in Microsoft’s alert:
Your XTM appliance should get this new IPS 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.
Microsoft has released patches to fix these vulnerabilities.
This alert was researched and written by Corey Nachreiner, CISSP (@SecAdept).