Some 64-bit operating systems and virtualization software programs are vulnerable to local privilege escalation attacks when running on Intel processors (CPUs), the U.S. Computer Emergency Readiness Team (US-CERT) said in a security advisory on Wednesday.The vulnerability is identified as CVE-2012-0217 and stems from the way Intel CPUs have implemented the SYSRET instruction in their x86-64 extension, known as Intel 64.Attackers could exploit the vulnerability to force Intel CPUs to return a general protection fault in privileged mode. This would allow them to execute code with kernel privileges from a least-privileged account, or to escape from a virtual machine and gain control of the host operating system.The vulnerability can only be exploited on Intel CPUs when the Intel 64 extension is in use. This means that 32-bit operating systems or virtualization software are not vulnerable.Some of the operating systems confirmed as vulnerable so far include x64-based versions of Windows 7 and Windows Server 2008 R2, the 64-bit versions of FreeBSD and NetBSD, the Xen virtualization software, as well as Red Hat Enterprise Linux and SUSE Linux Enterprise Server, which include the Xen hypervisor by default.The VMWare security response team confirmed that VMware's hypervisor does not make use of the SYSRET instruction and is, therefore, not vulnerable to this attack, US-CERT said.Most of the affected vendors have released security patches to address this vulnerability and users are advised to install them as soon as possible. Microsoft addressed it on Tuesday as part of its MS12-042 security bulletin.The privilege escalation attack is not applicable to AMD processors because they handle the SYSRET instruction differently, the Xen security team said in their advisory. However, under similar attack conditions, older AMD CPUs might lock up, resulting in a denial of service condition, the team said.