NTP is vulnerable to a denial of service, caused by an issue when relying on unauthenticated IPv4 time sources in ntpd. By predicting transmit timestamps for use in spoofed packets, a remote attacker could exploit this vulnerability to cause the daemon to crash or system time change.

A vulnerability was found in NTP. A security issue which enables an off-path attacker to prevent ntpd from synchronizing with NTP servers not using authentication. A server mode packet with spoofed source address sent to the client ntpd causes the next transmission to be rescheduled, even if the packet doesn't have a valid origin timestamp. If the packet is sent to the client frequently enough, it will stop polling the server and not be able to synchronize with it.

ntpd in ntp 4.2.8p10, 4.2.8p11, 4.2.8p12 and 4.2.8p13 allow remote attackers to prevent a broadcast client from synchronizing its clock with a broadcast NTP server via soofed mode 3 and mode 5 packets. The attacker must either be a part of the same broadcast network or control a slave in that broadcast network that can capture certain required packets on the attacker's behalf and send them to the attacker.

NTP is vulnerable to a denial of service, caused by a memory leak when a CMAC key is used and associated with a CMAC algorithm in the ntp.keys file in ntpd. By sending specially-crafted packets, a remote authenticated attacker could exploit this vulnerability to consume all available memory resources.