CVE-2016-9121: Inadequate Encryption Strength

go-jose before 1.0.4 suffers from an invalid curve attack for the ECDH-ES algorithm. When deriving a shared key using ECDH-ES for an encrypted message, go-jose neglected to check that the received public key on a message is on the same curve as the static private key of the receiver, thus making it vulnerable to an invalid curve attack.