ntp_request.c in ntpd in NTP before 4.2.4p8, and 4.2.5, allows remote attackers to cause a denial of service (CPU and bandwidth consumption) by using MODE_PRIVATE to send a spoofed (1) request or (2) response packet that triggers a continuous exchange of MODE_PRIVATE error responses between two NTP daemons.

Stack-based buffer overflow in the cookedprint function in ntpq/ntpq.c in ntpq in NTP before 4.2.4p7-RC2 allows remote NTP servers to execute arbitrary code via a crafted response.