The Linux kernel, as used in Red Hat Enterprise Linux 7, kernel-rt, and Enterprise MRG 2 and when booted with UEFI Secure Boot enabled, allows local users to bypass intended securelevel/secureboot restrictions by leveraging improper handling of secure_boot flag across kexec reboot.
https://github.com/mjg59/linux/commit/4b2b64d5a6ebc84214755ebccd599baef7c1b798
https://bugzilla.redhat.com/show_bug.cgi?id=1272472
http://www.securityfocus.com/bid/77097
http://www.openwall.com/lists/oss-security/2015/10/15/6