What the vulnerability does
01Description
Fedora CoreOS supports setting a GRUB bootloader password using a Butane config. When this feature is enabled, GRUB requires a password to access the GRUB command-line, modify kernel command-line arguments, or boot non-default OSTree deployments. Recent Fedora CoreOS releases have a misconfiguration which allows booting non-default OSTree deployments without entering a password. This allows someone with access to the GRUB menu to boot into an older version of Fedora CoreOS, reverting any security fixes that have recently been applied to the machine. A password is still required to modify kernel command-line arguments and to access the GRUB command line.
