The SSLv2 protocol, as used in OpenSSL before 1.0.1s and 1.0.2 before
1.0.2g and other products, requires a server to send a ServerVerify message
before establishing that a client possesses certain plaintext RSA data,
which makes it easier for remote attackers to decrypt TLS ciphertext data
by leveraging a Bleichenbacher RSA padding oracle, aka a "DROWN" attack.

 mdeslaur> openssl in Ubuntu is compiled with no-ssl2