As many experts anticipated, patches for the BootHole vulnerability in the GRUB2 bootloader that is used by all major Linux distributions are causing problems and preventing some users from booting their systems.

While the list of affected distros only included Red Hat yesterday, it has now expanded to include users of Ubuntu [1, 2, 3], Debian, CentOS [1, 2], and Fedora.

Microsoft security researcher Kevin Beaumont, also reports issues in cloud environments, namely where "a bug in cloud-init is causing problems across major cloud providers with Grub, such as Digital Ocean and Azure, having the same impact: patched systems then fail to boot."

Read more:

https://www.zdnet.com/article/boothole-fixes-causing-boot-problems-across-multiple-linux-distros/

https://arstechnica.com/gadgets/2020/07/red-hat-and-centos-systems-arent-booting-due-to-boothole-patches/