A vulnerability in MikroTik Version 6.38.5 could allow an unauthenticated remote attacker to exhaust all available CPU via a flood of UDP packets on port 500 (used for L2TP over IPsec), preventing the affected router from accepting new connections; all devices will be disconnected from the router and all logs removed automatically.
https://www.vulnerability-lab.com/get_content.php?id=2064
https://packetstormsecurity.com/files/142538/MikroTik-RouterBoard-6.38.5-Denial-Of-Service.html