A flaw was found in the Eclipse Californium Scandium package. This issue occurs when failing handshakes don't clean up counters for throttling, causing the threshold to be reached without being released again, resulting in a denial of service. An attacker could submit a high quantity of server requests, leaving the server unable to respond.

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 DTLSVERIFYPEERSONRESUMPTIONTHRESHOLD 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.

A flaw was found in californium. The certificate based (x509 and RPK) DTLS handshakes fails due to the DTLS server side being set to a wrong internal state by a previous certificate based DTLS handshake failure with TLS parameter mismatch. The highest threat from this vulnerability is to system availability.