Amazon Linux AMI Security Advisory: ALAS-2014-366
Advisory Release Date: 2014-09-19 10:27 Pacific
It was reported that the cmdmon protocol implemented in chrony was found to be vulnerable to DDoS attacks using traffic amplification. By default, commands are allowed only from localhost, but it's possible to configure chronyd to allow commands from any address. This could allow a remote attacker to cause a DoS, which could cause excessive resource usage.
Run yum update chrony to update your system.