Avoid Drive-by Downloads; Patch IE

Avoid Drive-by Downloads; Patch IE

Severity: High


  • These vulnerabilities affect: All current versions of Internet Explorer (IE)
  • How an attacker exploits them: By enticing one of your users to visit a malicious web page
  • 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


As part of today’s Patch Day, Microsoft released a security bulletin describing three new security vulnerabilities affecting Internet Explorer (IE). Technically, the new vulnerabilities seem only to affect IE 9 and 10, yet Microsoft has released the cumulative update for all versions. They rate this update as Critical.

Similar to last month, all three of these security flaws are “use after free” vulnerabilities, which are types of memory corruption flaws that attackers can leverage to execute arbitrary code. They all have to do with how IE handles various HTML objects. If an attacker can lure one of your users to a web page containing maliciously crafted HTML, he could exploit any one 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. Details 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 this kind of malicious web code. 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 and Intrusion Prevention services can often prevent these sorts of attacks, or the malware they try to distribute.

More specifically, our IPS signature team has developed a new signatures, which can detect and block at least one of these new IE vulnerabilities:

  • WEB-CLIENT Microsoft Internet Explorer Improper Ref Counting Use After Free (CVE-2012-4787)

Your appliance should get this new IPS update shortly.

Nonetheless, we still recommend you install Microsoft’s IE update to completely protect yourself from these vulnerabilities.


Microsoft has released patches to fix these vulnerabilities.


This alert was researched and written by Corey Nachreiner, CISSP.

Published with permission from WatchguardWire. Source.

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