CVE-2016-4955

ntpd in NTP 4.x before 4.2.8p8, when autokey is enabled, allows remote attackers to cause a denial of service (peer-variable clearing and association outage) by sending (1) a spoofed crypto-NAK packet or (2) a packet with an incorrect MAC value at a certain time.

Mitigation

Disable autokey authentication. Instead, configure ntp to use symmetric key authentication, or no authentication at all (if not required). To configure ntp with symmetric key authentication, follow the steps at <https://access.redhat.com/solutions/393663&gt;