PostgreSQL versions before 9.2.22, 9.3.18, 9.4.13, 9.5.8 and 9.6.4 are vulnerable to incorrect authentication flaw allowing remote attackers to gain access to database accounts with an empty password.
https://www.postgresql.org/about/news/1772/
https://security.gentoo.org/glsa/201710-06
https://access.redhat.com/errata/RHSA-2017:2860
https://access.redhat.com/errata/RHSA-2017:2728
https://access.redhat.com/errata/RHSA-2017:2678
https://access.redhat.com/errata/RHSA-2017:2677
http://www.securitytracker.com/id/1039142
http://www.securityfocus.com/bid/100278