A flaw double-free memory corruption in the Linux kernel HCI device initialization subsystem was found in the way user attach malicious HCI TTY Bluetooth device. A local user could use this flaw to crash the system. This flaw affects all the Linux kernel versions starting from 3.13.
https://lists.debian.org/debian-lts-announce/2021/06/msg00020.html
https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html