arch/x86/entry/entry_64.S in the Linux kernel before 4.1.6 on the x86_64 platform mishandles IRET faults in processing NMIs that occurred during userspace execution, which might allow local users to gain privileges by triggering an NMI. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-5157
