MySQL DB Causing Spike-up on Windows Server CPU
If not impacting business, have you tried to kill the connection app-side?

We had an issue with locked/active sessions from an app to a MSSQL DB, however the only way we could bypass was to break the active connection from the app to the DB via failover. That was only because it shifted resources from node 1 to node 2. We attempted to kill the connection via MSSQL queries but couldn't get it to stop that way, so failover ended up being the solution for us. 

Note: I am still new to DBA, but figured it's worth a try to share what I've experienced in my short time in this role.