op_host_enable() in src/zabbix_server/operations/operations.c:1272 passes the wrong value to the WHERE clause of its update. It passes the h->status where the h->hostid must be:

  if (HOST_STATUS_MONITORED != h->status)
  {
          zbx_db_execute("update hosts"
                          " set status=%d"
                          " where hostid=" ZBX_FS_UI64,
                          HOST_STATUS_MONITORED, h->status);

Impact:
  - Host stays disabled: the "Enable host" operation has no effect on the discovered or autoregistered host, so it is not monitored.
  - Wrong host can be changed: if a host with hostid=1 exists, it is enabled instead. If not, the update affects 0 rows and no error is reported.
  - Misleading audit log: zbx_audit_host_update_json_update_host_status() runs with the correct h->hostid, so the audit log shows the host as enabled when it wasn't.

Steps to reproduce:
  1. Create a host through network discovery or autoregistration, then disable it.
  2. Configure a discovery or autoregistration action with the "Enable host" operation.
  3. Trigger the action, for example by restarting the agent so it autoregisters again.
 
Expected result: the host's status becomes Enabled (hosts.status=0).