Debian Security Advisory 1948 ntp – denial of service

Robin Park and Dmitri Vinokurov discovered that the daemon component of the ntp package, a reference implementation of the NTP protocol, is not properly reacting to certain incoming packets.

An unexpected NTP mode 7 packets (MODE_PRIVATE) with spoofed IP data can lead ntpd to reply with a mode 7 response to the spoofed address. This may result in the service playing packet ping-pong with other ntp servers or even itself which causes CPU usage and excessive disk use due to logging. An attacker can use this to conduct denial of service attacks…

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