Security Advisory

NTP - CVE-2017-6462, CVE-2017-6451, CVE-2016-9042
Published: August 10, 2017
Last Update: January 25, 2021

In March, 2017, NTP.org[1] released a security advisory detailing a number of security issues. The following vulnerabilities reported in the NTP advisory are addressed in this document.

Item Score
# Vulnerability ID Source Score Summary
1 CVE-2017-6462 CVSS 3.0 7.8 High ntp: Buffer Overflow in DPTS Clock [2]
2 CVE-2017-6451 CVSS 3.0 7.8 High ntp: Improper use of snprintf() in mx4200_send()[3]
3 CVE-2016-9042 CVSS 3.0 4.4 Med ntp: DoS via origin timestamp check functionality [4, 5]
Affected Releases

The table below indicates releases of ACOS exposed to these vulnerabilities and ACOS releases that address these issues or are otherwise unaffected by them.

Customers using affected ACOS releases can overcome vulnerability exposures by updating to the indicated resolved release. If the table does not list a corresponding resolved or unaffected release, then no ACOS release update is currently available.

Releases Affected Releases Resolved or Unaffected
5.2.0 5.2.0-P1
5.0.0 – 5.1.0-P4 5.1.0-P5
4.1.4 – 4.1.4-GR1-P4 4.1.4-GR1-P5
4.1.2 – 4.1.2-P1 4.1.2-P2
4.1.1 – 4.1.1-P3 4.1.1-P4
4.1.100 – 4.1.100-P5 4.1.100-P5-SP1
4.1.0 – 4.1.0-P9 4.1.0-P10
3.2.3 – 3.2.5-P1 3.2.5-P2, 5.0.1-TPS
3.1.0-P1 – 3.2.1-P1 3.2.2-P1, 5.0.1-TPS
2.8.2 – 2.8.2-P8 4.1.2-P2, 4.1.4-GR1-P5, 5.1.0-P5, 5.2.0-P1
2.7.2 – 2.7.2-P11 4.1.0-P10, 4.1.1-P4, 4.1.4-GR1-P5, 5.1.0-P5, 5.2.0-P1
2.7.1-GR1 – 2.7.1-GR1-P1 4.1.0-P10, 4.1.1-P4, 4.1.4-GR1-P5, 5.1.0-P5, 5.2.0-P1
2.6.1-GR1 – 2.6.1-GR1-P16 4.1.0-P10, 4.1.1-P4, 4.1.4-GR1-P5, 5.1.0-P5, 5.2.0-P1
Workarounds and Mitigations

Common security best practices in the industry for network appliance management and control planes can enhance protection against remote malicious attacks. Limit the exploitable attack surface for critical, infrastructure, networking equipment through the use of access lists or firewall filters to and from only trusted, administrative networks or hosts.

Software Updates

Software updates that address these vulnerabilities are or will be published at the following URL:

Vulnerability Details

The following table shares brief descriptions for the vulnerabilities addressed in this document.

Vulnerability ID Vulnerability Description

Buffer overflow in the legacy Datum Programmable Time Server (DPTS) refclock driver in NTP before 4.2.8p10 and 4.3.x before 4.3.94 allows local users to have unspecified impact via a crafted /dev/datum device.


The mx4200_send function in the legacy MX4200 refclock in NTP before 4.2.8p10 and 4.3.x before 4.3.94 does not properly handle the return value of the snprintf function, which allows local users to execute arbitrary code via unspecified vectors, which trigger an out-of-bounds memory write.


An exploitable denial of service vulnerability exists in the origin timestamp check functionality of ntpd 4.2.8p9. A specially crafted unauthenticated network packet can be used to reset the expected origin timestamp for target peers. Legitimate replies from targeted peers will fail the origin timestamp check (TEST2) causing the reply to be dropped and creating a denial of service condition. This vulnerability can only be exploited if the attacker can spoof all of the servers.

Modification History
Revision Date Description
1.0 April 18, 2018

Created web page

2.0 October 11, 2019

Added 4.1.100 release family.

3.0 July 27, 2020

Added 4.1.4, 5.x release families, update resolved versions

4.0 January 22, 2021

Added 3.2.3-5, 5.0.1-TPS release families, update resolved versions

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