An ACL bypass flaw was found in pacemaker. An attacker having a local account on the cluster and in the haclient group could use IPC communication with various daemons directly to perform certain tasks that they would be prevented by ACLs from doing if they went through the configuration.
https://security.gentoo.org/glsa/202309-09
https://seclists.org/oss-sec/2020/q4/83
https://lists.debian.org/debian-lts-announce/2021/01/msg00007.html
https://lists.clusterlabs.org/pipermail/users/2020-October/027840.html