Amazon Linux AMI Security Advisory: ALAS-2017-875
Advisory Release Date: 2017-09-14 22:22 Pacific
Information leak when SSSD is used for authentication against remote server:
A flaw was found where authconfig could configure sssd in a way that treats existing and non-existing logins differently, leaking information on existence of a user. An attacker with physical or network access to the machine could enumerate users via a timing attack.(CVE-2017-7488 )
Run yum update authconfig to update your system.