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.