Some of the servers that expose TLS to cross-protocol DROWN attacks via SSLv2 are MTAs running Postfix. If you're using an older Postfix release (released prior to July 20 2015), or you've explicitly configured TLS settings that may have enabled SSLv2, please update your configuration as suggested below:
# Minimal recommended settings. Whenever the built-in defaults are # sufficient, let the built-in defaults stand by deleting any explicit # overrides. The default mandatory TLS protocols have never included # SSLv2, check to make sure you have not inadvertently enabled it. # smtpd_tls_protocols = !SSLv2, !SSLv3 smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3 tlsproxy_tls_protocols = $smtpd_tls_protocols tlsproxy_tls_mandatory_protocols = $smtpd_tls_mandatory_protocols smtp_tls_protocols = !SSLv2, !SSLv3 smtp_tls_mandatory_protocols = !SSLv2, !SSLv3 lmtp_tls_protocols = !SSLv2, !SSLv3 lmtp_tls_mandatory_protocols = !SSLv2, !SSLv3 smtpd_tls_ciphers = medium smtp_tls_ciphers = medium # Other best practices # Strongly recommended: # http://www.postfix.org/FORWARD_SECRECY_README.html#server_fs # (Note, before applying the setting below, you'll need to create # the dh2048.pem parameter file as described in FORWARD_SECRECY_README) # smtpd_tls_dh1024_param_file=${config_directory}/dh2048.pem smtpd_tls_eecdh_grade = strong # Suggested, not strictly needed: # smtpd_tls_exclude_ciphers = EXPORT, LOW, MD5, SEED, IDEA, RC2 smtp_tls_exclude_ciphers = EXPORT, LOW, MD5, aDSS, kECDHe, kECDHr, kDHd, kDHr, SEED, IDEA, RC2 -- Viktor.
