According to the researcher, "DROWN" is a new form of cross-protocol Bleichenbacher padding oracle attack. An attacker using "DROWN" may obtain the session key from a vulnerable server supporting SSLv2 and use it to decrypt any traffic encrypted using the shared certificate.

It allows an attacker to decrypt intercepted TLS connections by making specially crafted connections to an SSLv2 server that uses the same private key."



The SSLv2 protocol is the only protocol directly impacted; however, the researcher's website states that many servers may use a shared certificate between the SSLv2 and the newer TLS protocols. If so, if the certificate is decrypted via SSLv2, then the TLS protocol using the shared certificate can be decrypted as well. The attack requires approximately 1000 SSL handshakes to be intercepted for the attack to be effective.



The researchers have also released a DROWN attack check tool and an FAQ that provides more complete information.