OpenSMTPD has released version 6.6.4p1 to address a critical
vulnerability. A remote attacker could exploit this vulnerability to take
control of an affected server. OpenSMTPD is an open-source server-side
implementation of the Simple Mail Transfer Protocol (SMTP) that is part of the
Bulgaria encourages users and administrators to apply the necessary
update. For OpenBSD implementations, binary patches are available through
syspatch; see OpenSMTPD’s Message 04888 for further instruction.