Microsoft has rushed out a temporary fix to address ongoing attacks targeting an Internet Explorer zero-day vulnerability.
The software giant said the Fix-It temporary workaround should be effective in preventing a successful attack. The company said the vulnerability impacts all currently supported versions of the browser, but attacks have been limited to users of Internet Explorer 8 and Internet Explorer 9.
"On completion of this investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs," the company said in a security advisory issued Tuesday.
"In addition, we are actively working with partners to monitor the threat landscape and take action against malicious sites that attempt to exploit this vulnerability."
The fact that Microsoft is rushing out a patch so quickly indicates the threat is serious, said Paul Henry, security and forensic analyst at Lumension. Cybercriminals can set up drive-by attack campaigns or lure victims to a website hosting malware that targets the coding error.
"This seems to be perfectly positioned for drive-by malware using compromised websites," Henry told CRN US. "Since these are targeted attacks, someone is restricting use of it; they don't want information about this out in the wild because they want to be able to profit from it or use it in nation-state attacks."
The attack is very targeted and limited to Japan, according to Wolfgang Kandek, chief technology officer of Qualys.
"It might not affect you at the moment. But with the publication of the shim, other attackers can now analyse the condition fixed and will be able to produce an equivalent exploit fairly quickly," Kandek wrote in a blog post about the issue. "We suggest applying the Fix-It as soon as possible if you use IE to access the Internet."
The flaw stems from an error in the way the browser accesses an object in memory that has been deleted or has not been properly allocated. The coding error results in memory corruption, giving an attacker the ability to execute code in the context of the current user within Internet Explorer, Microsoft said.
As part of its September 2013 Patch Tuesday updates, Microsoft repaired 47 vulnerabilities, including 10 critical flaws in Internet Explorer.