The Network Time Protocol (NTP) is used to synchronize a computer's time with a referenced time source.
It was discovered that ntpd as a client did not correctly check the originate timestamp in received packets. A remote attacker could use this flaw to send a crafted packet to an ntpd client that would effectively disable synchronization with the server, or push arbitrary offset/delay measurements to modify the time on the client. (CVE-2015-8138)
All ntp users are advised to upgrade to these updated packages, which contain a backported patch to resolve this issue. After installing the update, the ntpd daemon will restart automatically.