nbd_add_socket in drivers/block/nbd.c in the Linux kernel through 5.10.12 has an ndb_queue_rq use-after-free that could be triggered by local attackers (with access to the nbd device) via an I/O request at a certain point during device setup, aka CID-b98e762e3d71.
https://www.openwall.com/lists/oss-security/2021/01/28/3
https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html