Ubuntu: USN-3390-1 (CVE-2017-7546): PostgreSQL vulnerabilities

Ben de Graaff, Jelte Fennema, and Jeroen van der Ham discovered that
PostgreSQL allowed the use of empty passwords in some authentication
methods, contrary to expected behaviour. A remote attacker could use an
empty password to authenticate to servers that were believed to have
password login disabled. (CVE-2017-7546)

Jeff Janes discovered that PostgreSQL incorrectly handled the
pg_user_mappings catalog view. A remote attacker without server privileges
could possibly use this issue to obtain certain passwords. (CVE-2017-7547)

Chapman Flack discovered that PostgreSQL incorrectly handled lo_put()
permissions. A remote attacker could possibly use this issue to change the
data in a large object. (CVE-2017-7548)