californium

In Eclipse Californium version 2.3.0 to 2.6.0, the certificate based (x509 and RPK) DTLS handshakes accidentally fails, because the DTLS server side sticks to a wrong internal state. That wrong internal state is set by a previous certificate based DTLS handshake failure with TLS parameter mismatch. The DTLS server side must be restarted to recover this. This allow clients to force a DoS.

In Eclipse Californium version 2.0.0 to 2.7.2 and 3.0.0-3.5.0 a DTLS resumption handshake falls back to a DTLS full handshake on a parameter mismatch without using a HelloVerifyRequest. Especially, if used with certificate based cipher suites, that results in message amplification (DDoS other peers) and high CPU load (DoS own peer). The misbehavior occurs only with DTLS_VERIFY_PEERS_ON_RESUMPTION_THRESHOLD values larger than 0.

In Eclipse Californium version 2.0.0 to 2.6.4 and 3.0.0-M1 to 3.0.0-M3, the certificate based (x509 and RPK) DTLS handshakes accidentally succeeds without verifying the server side's signature on the client side, if that signature is not included in the server's ServerKeyExchange.