Race condition in OpenVPN before 2.0.1, when --duplicate-cn is not enabled, allows remote attackers to cause a denial of service (server crash) via simultaneous TCP connections from multiple clients that use the same client certificate.

OpenVPN before 2.0.1 does not properly flush the OpenSSL error queue when a packet can not be decrypted by the server, which allows remote authenticated attackers to cause a denial of service (client disconnection) via a large number of packets that can not be decrypted.

OpenVPN before 2.0.1, when running with "verb 0" and without TLS authentication, does not properly flush the OpenSSL error queue when a client fails certificate authentication to the server and causes the error to be processed by the wrong client, which allows remote attackers to cause a denial of service (client disconnection) via a large number of failed authentication attempts.