Ken Gaillot discovered a vulnerability in the Pacemaker cluster
resource manager: If ACLs were configured for users in the "haclient"
group, the ACL restrictions could be bypassed via unrestricted IPC communication, resulting in cluster-wide arbitrary code execution with
If the "enable-acl" cluster option isn't enabled, members of the
"haclient" group can modify Pacemaker's Cluster Information Base without restriction, which already gives them these capabilities, so there is
no additional exposure in such a setup.
For the stable distribution (buster), this problem has been fixed in
We recommend that you upgrade your pacemaker packages.