IE Update Fixes Two Zero Day Vulnerabilities

Severity: High

Summary:

• These vulnerabilities affect: All current versions of Internet Explorer (IE)
• How an attacker exploits them: By enticing one of your users to visit a web page containing malicious content
• Impact: An attacker can execute code on your user’s computer, often gaining complete control of it
• What to do: Install Microsoft’s IE updates immediately, or let Windows Automatic Update do it for you

Exposure:

As part of today’s Patch Day, Microsoft released a security bulletin describing ten vulnerabilities affecting Internet Explorer (IE); including two that attackers have been exploiting in the wild.

On it’s surface, this bulletin looks very similar to many of Microsoft’s past IE bulletins.  It describes ten “memory corruption” vulnerabilities, which share the same scope and impact. If an attacker can lure one of your users to a web page containing maliciously crafted content, he can exploit any of these vulnerabilities to execute code on that user’s computer, inheriting that user’s privileges. Since Windows users often have local administrative privileges, attackers can leverage these issues to gain complete control of their machines.

However, today’s IE update differs slightly in that it fixes two zero day vulnerabilities that attackers are exploiting in the wild. We’ve warned you about the first in a previous post, and just learned about a second one today.

These remote code execution flaws pose significant risk to IE users, especially the two zero day ones. Attackers can exploit them to launch drive-by download attacks, and we’ve already seen them doing so with two of these vulnerabilities. If you use IE, you should download and install Microsoft’s cumulative update immediately.

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 September 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 many of the memory corruption vulnerabilities described in Microsoft’s alert:

• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3897)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3875)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3871)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3886)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3885)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3874)
• WEB-CLIENT Microsoft Internet Explorer Memory Corruption Vulnerability (CVE-2013-3873)

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:

• MS Security Bulletin MS13-080

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