A flaw was found in the Linux kernel's Layer 2 Tunneling Protocol (L2TP). A missing lock when clearing sk_user_data can lead to a race condition and NULL pointer dereference. A local user could use this flaw to potentially crash the system causing a denial of service.
https://lore.kernel.org/netdev/20221121085426.21315-1-jakub%40cloudflare.com/t
https://lore.kernel.org/all/20221114191619.124659-1-jakub%40cloudflare.com/t
https://lists.debian.org/debian-lts-announce/2023/05/msg00005.html