cloud-init through 25.1.2 includes the systemd socket unit cloud-init-hotplugd.socket with default SocketMode that grants 0666 permissions, making it world-writable. This is used for the "/run/cloud-init/hook-hotplug-cmd" FIFO. An unprivileged user could trigger hotplug-hook commands.
Exploitability
AV:LAC:LPR:NUI:NScope
S:UImpact
C:LI:LA:L5.9/CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L