Public Date:
1340858: CVE-2016-4955 ntp: autokey association reset

The MITRE CVE dictionary describes this issue as:

ntpd in NTP 4.x before 4.2.8p8, when autokey is enabled, allows remote attackers to cause a denial of service (peer-variable clearing and association outage) by sending (1) a spoofed crypto-NAK packet or (2) a packet with an incorrect MAC value at a certain time.

Find out more about CVE-2016-4955 from the MITRE CVE dictionary dictionary and NIST NVD.

CVSS v2 metrics

NOTE: The following CVSS v2 metrics and score provided are preliminary and subject to review.

Base Score 2.6
Base Metrics AV:N/AC:H/Au:N/C:N/I:N/A:P
Access Vector Network
Access Complexity High
Authentication None
Confidentiality Impact None
Integrity Impact None
Availability Impact Partial

Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 7 ntp Will not fix
Red Hat Enterprise Linux 6 ntp Will not fix
Red Hat Enterprise Linux 5 ntp Will not fix


This issue was discovered by Miroslav Lichvar (Red Hat).


Disable autokey authentication. Instead, configure ntp to use symmetric key authentication, or no authentication at all (if not required). To configure ntp with symmetric key authentication, follow the steps at

External References

Last Modified

CVE description copyright © 2017, The MITRE Corporation