There is an issue with grub2 before version 2.06 while handling symlink on
ext filesystems. A filesystem containing a symbolic link with an inode size
of UINT32_MAX causes an arithmetic overflow leading to a zero-sized memory
allocation with subsequent heap-based buffer overflow.

Chris Coulson discovered that multiple integer overflows existed in
GRUB2 when handling certain filesystems, font files or PNG images,
leading to heap-based buffer overflows. A local attacker could
use these to execute arbitrary code and bypass UEFI 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