A flaw was found in grub2 in versions prior to 2.06. The rmmod implementation allows the unloading of a module used as a dependency without checking if any other dependent module is still loaded leading to a use-after-free scenario. This could allow arbitrary code to be executed or a bypass of Secure Boot protections. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective
https://security.netapp.com/advisory/ntap-20220325-0001/