New zero-day vulnerability in Windows 7 64-bit may allow remote code execution

Microsoft is investigating reports that visiting a malicious Web page using Safari can crash vulnerable Windows systems

Microsoft is currently investigating reports of a zero-day vulnerability in Windows 7 64-bit that leads to crashes and could allow attackers to execute arbitrary code on affected systems.

The security flaw can be exploited by opening a Web page containing a specially crafted iframe using Apple's Safari browser.

[ The Web browser is your portal to the world -- as well as the conduit that lets in many security threats. InfoWorld's expert contributors show you how to secure your Web browsers in this "Web Browser Security Deep Dive" PDF guide. ]

Twitter user WebDEViL reported that the flaw can crash a system, triggering the "blue screen of death".

Security researchers from Secunia believe that the crash could also be leveraged to execute malicious code.

"Based on our testing the impact could be more severe due to the type of crash and nature of the vulnerability i.e. crashing when attempting to write to invalid memory in a call to memmove()," said Secunia's chief security specialist Carsten Eiram. "Based on this we do consider remote code execution a possibility though it has not been proven at this time."

The security flaw stems from an error in the win32k.sys kernel-mode driver, a common source for critical Windows vulnerabilities.

The exploit has so far only been confirmed on Windows 7 64-bit when parsing an iframe with an overly-long height attribute in Safari.

However, researchers don't exclude the possibility that other versions of Windows can be affected through different attack vectors. "Other 64-bit versions could be affected," Eiram said.

"During testing we observed no crashes on Windows XP SP3 32-bit nor Windows 7 32-bit, but cannot completely rule out that these could be affected via different approaches." he added.

Microsoft is aware of the reports, but hasn't published an advisory yet. "We are currently examining the issue and will take appropriate action to help ensure customers are protected," said Jerry Bryant, manager of response communications with Microsoft's Trustworthy Computing Group.