This indicates an attack attempt to exploit a Buffer Overflow Vulnerability in NTP Daemon.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted NTP response. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted NTP response.
ntp.org NTP prior to ntp-4.2.8p11
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor: