OpenVPN Access Server 2.10 and prior versions are susceptible to resending multiple packets in a response to a reset packet sent from the client which the client again does not respond to, resulting in a limited amplification attack.
OpenVPN Access Server older than version 2.8.4 and version 2.9.5 generates new user authentication tokens instead of reusing exiting tokens on reconnect making it possible to circumvent the initial token expiry timestamp.