Redmond slips out temporary emergency fix for IE 0-day

Stepping outside its normal Patch Tuesday cycle, Microsoft has rolled out an emergency fix to an Internet Explorer bug that was under active malware attack.

This advisory provides access to “Fix it For Me”, with a more detailed outline of the CVE-2013-3893 vulnerability here. All versions of IE 6 to 10 are affected.

As Microsoft writes, the vulnerability “exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated. The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer. An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website.”

The current temporary fix is designed to prevent exploitation of the bug, with a permanent fix presumably to follow. In this TechNet post, Microsoft's Dustin Childs writes that IE users should take further action:

• Set Internet and local intranet security zone settings to "High" to block ActiveX Controls and Active Scripting in these zones;
• Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and local intranet security zones.

Childs notes that both of these actions “may affect usability” and suggests adding trusted sites to the Internet Explorer Trusted zone.

Since the stopgap “Fix It” patch isn't being rolled out automatically, users have to take their courage in their own hands and download it themselves. ®