Out-of-Cycle Word FixIt Corrects Zero Day Vulnerability

If you’re worried about spear phishing attacks (and if you’re not, you should be), grab Microsoft’s emergency FixIt to mitigate a zero day vulnerability attackers are exploiting in the wild.

In a security advisory released yesterday, Microsoft warned of a zero day vulnerability in Word, which attackers are exploiting in what Microsoft describes as limited, targeted attacks. Apparently, the exploit in the wild targets Word 2010, but the flaw affects other versions of Word as well. Since this is an early advisory, it doesn’t describe the flaw in much technical detail. However, it does mention attackers can trigger the flaw with specially crafted rich text format (RTF) files. If an attacker can entice you to view a malicious RTF in Word, he could exploit this vulnerability to execute code on you computer, with your privileges. If you are an administrator, the attacker gains complete control of your PC.

By default, most current version of Office use Word as Outlook’s email viewer. This mean attackers can trigger this flaw just by getting you to open an RTF attached to an email. According to some on Twitter, simply previewing an email with a malicious RTF triggers the flaw.

While Microsoft hasn’t had time to release a full patch yet, they have posted a FixIt that mitigates the risk of this vulnerability. If you use Office, I highly recommend you install the FixIt as soon as you can. Also, Microsoft’s Enhanced Mitigation Experience Toolkit (EMET) can mitigate the risk of any type of memory corruption flaw. In general, I recommend you install EMET on Windows machines to protect them from any zero day, memory-related issues.

I’ll post more details about this flaw during an upcoming Patch Day, when Microsoft releases the final update. In the meantime, if you’d like more information about it you can check out Microsoft’s security blog post. — Corey Nachreiner, CISSP (@SecAdept

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