An unprivileged write to the file handler flaw in the Linux kernel's control groups and namespaces subsystem was found in the way users have access to some less privileged process that are controlled by cgroups and have higher privileged parent process. It is actually both for cgroup2 and cgroup1 versions of control groups. A local user could use this flaw to crash the system or escalate their privileges on the system.

A flaw was found in the Linux kernel. A incorrect size check in decodenfsfh() may lead to an overwrite of 2 bytes beyond destination.

References:

https://lore.kernel.org/lkml/20210517140244.822185482@linuxfoundation.org/