Microsoft IE Zero-Day Vulnerability Exploited in the Wild

All Internet Explorer versions are at risk, including unsupported Windows XP users.

Microsoft is warning its users about a new unpatched security vulnerability that affects multiple versions of the Internet Explorer Web browser. Microsoft issued security advisory 2963983 on April 26, detailing the flaw that is now identified as CVE-2014-1776.

The impact of CVE-2014-1776 is widespread in that IE versions 6, 7, 8, 9, 10 and 11 are all at risk from the remote code execution vulnerability.

"The vulnerability exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated," Microsoft warns in its advisory. "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."

Microsoft admits in its advisory that it is aware of targeted attacks that are currently attempting to exploit the vulnerability. Microsoft credits security research firm FireEye with helping to discover and report the flaw.

In a blog post, FireEye researchers note that while CVE-2014-1776 affects IE versions 6 through 11, so far attackers have only been targeting IE 9 though IE 11.

"The exploit leverages a previously unknown use-after-free vulnerability, and uses a well-known Flash exploitation technique to achieve arbitrary memory access and bypass Windows' ASLR and DEP protections," FireEye explained in its analysis.

Windows ASLR (Address Space Layout Randomization) and DEP (Data Execution Prevention) are techniques used within Windows operating systems to protect against the unauthorized use of memory space. Microsoft has technology that provides additional memory protection that goes beyond the capabilities offered in ASLR and DEP, as part of the Enhanced Mitigation Experience Toolkit (EMET).

EMET is an optional download for Windows users and, as such, is not on all Microsoft Windows installations by default. Both Microsoft and FireEye recommend the use EMET as a way to mitigate the risk from the CVE-2014-1776 vulnerability. Going a step further, FireEye recommends that IE users disable the Adobe Flash plug-in, without which the CVE-2014-1776 exploit will not work.

The new zero-day vulnerability is the first to be publicly reported since Microsoft ended support for Windows XP during the April 8 Patch Tuesday update. As such, it's not likely that a patch will be made available for Windows XP users for the CVE-2014-1776 vulnerability.

"On completion of our 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," Microsoft stated in its advisory.

The new zero-day vulnerability in IE is not the first that Microsoft has had to deal with in 2014. On Feb. 13, FireEye reported the CVE-2014-0322 IE security vulnerability. Microsoft did not patch that issue until March 11.

Beyond the CVE-2014-1776 vulnerability, Microsoft still has yet to patch a pair of security vulnerabilities first reported at the Pwn2own browser hacking event sponsored by Hewlett-Packard's Zero Day Initiative (ZDI). In contrast with the new CVE-2014-1776 vulnerability, the details of the Pwn2own vulnerabilities have been kept private.

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist.

Sean Michael Kerner

Sean Michael Kerner

Sean Michael Kerner is an Internet consultant, strategist, and contributor to several leading IT business web sites.