NTP - CVE-2016-7429, CVE-2016-7433

Published on July 27th, 2017 | Last Update: July 27th, 2017



In November, 2016, NTP.org 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-2016-7429 CVSS 3.0 3.7 Low ntpd Rx server response from spoof on wrong I/F [1, 2]
2 CVE-2016-7433 CVSS 3.0 5.3 Medium ntpd bug - jitter value higher than expected [1, 3]


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
  4.1.2 (a)
4.1.1 – 4.1.1-P1 4.1.1-P2
4.1.0 – 4.1.0-P9 4.1.0-P10
3.1.0-P1 – 3.2.1-P1 3.2.2-P1
2.8.2 – 2.8.2-P8 4.1.2
2.7.2 – 2.7.2-P11 4.1.0-P10, 4.1.1-P2
2.7.1-GR1 – 2.7.1-GR1-P1 4.1.0-P10, 4.1.1-P2
2.6.1-GR1 – 2.6.1-GR1-P16 4.1.0-P10, 4.1.1-P2

(a) Including all updates to the release(s).



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



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

Vulnerability ID Description
CVE-2016-7429   NTP before 4.2.8p9 changes the peer structure to the interface it receives the response from a source, which allows remote attackers to cause a denial of service (prevent communication with a source) by sending a response for a source to an interface the source does not use.
CVE-2016-7433   NTP before 4.2.8p9 does not properly perform the initial sync calculations, which allows remote attackers to unspecified impact via unknown vectors, related to a "root distance that did not include the peer dispersion."



Ref # General Link
[1] November 2016 ntp-4.2.8p9 NTP Security Vulnerability Announcement
[2] NIST NVD, CVE-2016-7429
[3] NIST NVD, CVE-2016-7433






Revision Date Description
1.0 2017-07-27 Initial Publication
Thursday, July 27, 2017