Unlike Heartbleed, the actual private key is not leaked to the attacker. Rather, a SSLv2-enabled server allows you to build an oracle with which you can decrypt

Unlike Heartbleed, the actual private key is not leaked to the attacker. Rather, a SSLv2-enabled server allows you to build an oracle with which you can decrypt a TLS connection (modern crypto, secure, etc.) to a server that uses the same key. With Perfect Forward Secrecy, any DROWN compromise is limited to the period where an attacker is actively running the attack against you. Previous PFS sessions cannot be decrypted. Without PFS, I'm not sure, but my gut feeling is that previous traffic could be decrypted if someone actively attacks you on an unpatched system now.