NTP BUG 3114: Broadcast Mode Replay Prevention DoS

Last update: April 22, 2024 18:49 UTC (7e7bd5857)


Resolved 4.2.8p9 21 Nov 2016
References Bug 3114 CVE-2016-7427
Affects ntp-4.2.8p6, up to but not including ntp-4.2.8p9,
and ntp-4.3.90 up to, but not including ntp-4.3.94
Resolved in 4.2.8p9.
CVSS2 Score LOW 3.3 AV:A/AC:L/Au:N/C:N/I:N/A:P
CVSS3 Score MED 4.3 CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L


The broadcast mode of NTP is expected to only be used in a trusted network. If the broadcast network is accessible to an attacker, a potentially exploitable denial of service vulnerability in ntpd’s broadcast mode replay prevention functionality can be abused. An attacker with access to the NTP broadcast domain can periodically inject specially crafted broadcast mode NTP packets into the broadcast domain which, while being logged by ntpd, can cause ntpd to reject broadcast mode packets from legitimate NTP broadcast servers.



This weakness was discovered by Matthew Van Gundy of Cisco.