Assume that you use AlwaysOn Availability Groups on an instance of Microsoft SQL Server 2017 that's managed by an external cluster technology for high availability and disaster recovery (for example, Pacemaker on Linux.) When the external cluster fails over the primary server to another server that's running SQL Server, the original primary server doesn't quit as expected. Therefore, a split-brain scenario occurs.
This problem is fixed in the following cumulative update for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server: