According to The U.S. Computer Emergency Readiness Team, a flaw has been discovered in Intel chips that would allow hackers to execute malicious code on a variety of 64-bit operating systems. The flaw is limited to chips using SYSRET instruction. Intel has made no comment on the disclosure.

"Some 64-bit operating systems and virtualization software running on Intel CPU hardware are vulnerable to a local privilege escalation attack. The vulnerability may be exploited for local privilege escalation or a guest-to-host virtual machine escape," says the US-CERT.

Several x64-based operating systems like Windows 7, Windows Server 2008 R2, 64-bit FreeBSD, 64-bit NetBSD, as well as systems that include the Xen hypervisor, are exposed to this vulnerability.

While 32-bit operating systems are safe, Intel CPUs that use the Intel 64 extension need the security patches released by Microsoft in their MS12-042 security bulletin.

The VMware virtualization software does not seem affected by the vulnerability as its hypervisor doesn't use the SYSRET instruction, making the virtualization solution safe from attacks. AMD is also on the list of vendors not affected by the privileged escalation exposure issued by US-CERT. Because the SYSRET instruction is handled differently on AMD CPUs, the CVE-2012-0217 vulnerability does not apply to these chips.

The U.S. Computer Emergency Readiness Team (US-CERT) issued a security advisory in which it thoroughly details the vulnerability.