Red Hat’s Product Security team is working with OSS-security to get a CVE listed for the below patch. Excerpting the OSS-security request from Wade Mealing of Red Hat, which was in turn paraphrased from Linn Crosetto, perhaps others:
When the kernel was booted with UEFI Secure Boot enabled, securelevel is set. If kexec (either through crash or admin action) is then used to load the same kernel, after reboot securelevel is disabled. In this state, the system is missing the protections provided by securelevel, for example kexec may be used to load an unsigned kernel via the legacy system call kexec_load. In the securelevel patchset, the state of UEFI Secure Boot is queried in the EFI stub, and sets a boot_params flag to indicate the state of UEFI Secure Boot. This flag is then used in setup_arch() to determine the correct state of securelevel. If the kernel is not booted via the EFI stub, securelevel is not set even if UEFI Secure Boot is enabled.
TLDR: this allows a bypass the security mechanism of securelevel/secureboot combination.
This patchset affects Red Hat specific kernels as secureboot is not fully fully implemented upstream yet.
It appears you need an account to view the bug database entry, and the patch: