In PostgreSQL 9.3.x before 9.3.17, 9.4.x before 9.4.12, 9.5.x before 9.5.7, and 9.6.x before 9.6.3, it was found that the PGREQUIRESSL environment variable was no longer enforcing a SSL/TLS connection to a PostgreSQL server. An active Man-in-the-Middle attacker could use this flaw to strip the SSL/TLS protection from a connection between a client and a server.
www.debian.org/security/2017/dsa-3851
www.securityfocus.com/bid/98461
www.securitytracker.com/id/1038476
access.redhat.com/errata/RHSA-2017:1677
access.redhat.com/errata/RHSA-2017:1678
access.redhat.com/errata/RHSA-2017:1838
access.redhat.com/errata/RHSA-2017:2425
security.gentoo.org/glsa/201710-06
www.postgresql.org/about/news/1746/