GRUB2 fails to validate kernel signature when booted directly without shim,
allowing secure boot to be bypassed. This only affects systems where the
kernel signing certificate has been imported directly into the secure boot
database and the GRUB image is booted directly without the use of shim.
This issue affects GRUB2 version 2.04 and prior versions.

Mathieu Trudel-Lapierre discovered that in certain situations,
GRUB2 failed to validate kernel signatures. A local attacker could
use this to bypass Secure Boot restrictions.

amurray

grub2-signed is not supported in Ubuntu 12.04 ESM (precise/esm) and so marking the priority for grub2 in this release as low