This patch will will introduce a new ssl server option: require_endpoint_verification.
Setting it will enable hostname verification for inter-node SSL communication. This is necessary to prevent man-in-the-middle attacks when building a trust chain against a common CA. See here for background details.
Clusters that solely rely on importing all node certificates into each trust store (as described here) are not effected.
Clusters that use the same common CA to sign node certificates are potentially affected. In case the CA signing process will allow other parties to generate certs for different purposes, those certificates could in turn be used for MITM attacks. The provided patch will allow to enable hostname verification to make sure not only to check if the cert is valid but also if it has been created for the host that we're about to connect.
Corresponding dtest: Test for CASSANDRA-9220