GRUB2 enables the use of the command acpi even when secure boot is signaled by the firmware. An attacker with local root privileges can drop a small SSDT in /boot/efi and modify grub.cfg to instruct grub to load said SSDT. The SSDT then gets run by the kernel and it overwrites the kernel lockdown configuration enabling the attacker to load unsigned kernel modules and kexec unsigned code.
GRUB2 enables the use of the command acpi even when secure boot is signaled by the firmware. An attacker with local root privileges can drop a small SSDT in /boot/efi and modify grub.cfg to instruct grub to load said SSDT. The SSDT then gets run by the kernel and it overwrites the kernel lockdown configuration enabling the attacker to load unsigned kernel modules and kexec unsigned code.
https://lists.gnu.org/archive/html/grub-devel/2021-03/msg00007.html https://git.savannah.gnu.org/gitweb/?p=grub.git;a=commit;h=3e8e4c0549240fa209acffceb473e1e509b50c95
Vulmon