Microsoft Fixes 19 Remote Code Execution Flaws in IE

Severity: High

Summary:

• These vulnerabilities affect: Most 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 19 new security vulnerabilities affecting Internet Explorer (IE). Microsoft describes almost all of these flaws as “memory corruption” vulnerabilities, but they don’t specify the exact type of memory corruption flaw. Being that we’ve seen a lot of “use after free” vulnerabilities (one type of memory corruption issue) in IE lately, I wouldn’t be surprised if many of these vulnerabilities fell into that class of flaw.

Regardless of which type of memory corruption flaws these are, they all share the same scope and impact. 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.

If you’d like more technical detail about these flaws, see the “Vulnerability Information” section of Microsoft’s bulletin. Technicalities aside, all of these remote code execution flaws pose significant risk to IE users, and allow attackers to launch drive-by download attacks. Attackers often hijack legitimate web sites and force them to serve malicious web code in something the industry calls a “watering hole” attack. So these types of flaws may affect you even when visiting legitimate, trusted web sites.

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 IE security bulletin.

For All WatchGuard Users:

WatchGuard’s Gateway Antivirus services can often prevent the malware that drive-by download attacks try to force onto your computer. Furthermore, our Reputation Enabled Defense (RED) and WebBlocker service can often prevent your users from accidentally visiting malicious sites. Nonetheless, we still recommend you install Microsoft’s IE update to completely protect yourself from these vulnerabilities.

Status:

Microsoft has released patches to fix these vulnerabilities.

References:

• MS Security Bulletin MS13-047

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

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