grub2: GRand Unified Bootloader - grub2-signed: GRand Unified Bootloader Details: USN-4432-1 fixed vulnerabilities in GRUB2 affecting Secure Boot environments. Unfortunately, the update introduced regressions for some BIOS systems , preventing them from successfully booting. This update addresses the issue. Users with BIOS systems that installed GRUB2 versions from USN-4432-1 should verify that th ...