# CVE-2016-9311: NTP Project ntpd denial of service in trap service

Source: https://junglewise.ai/threats/cve-2016-9311-ntp-project-ntpd-denial-of-service-in-trap-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-13. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-9311 · Severity: medium · CVSS 5.9 · Published 2017-01-13

A vulnerability in the Network Time Protocol (NTP) service could allow a remote attacker to crash the system's time-synchronization daemon. This service is critical for ensuring all computers on a network share the same accurate time for logging and security purposes. An exploit would result in a denial of service, potentially causing issues with time-sensitive applications and security protocols.

Technologies: [Ntp](https://junglewise.ai/threats/technologies/ntp), [NTP Project Ntpd](https://junglewise.ai/threats/technologies/ntpd). Vendors: [Ntp](https://junglewise.ai/threats/vendors/ntp), [NTP Project](https://junglewise.ai/threats/vendors/ntp-project).

## Quick answers

**Is CVE-2016-9311 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9311 being exploited in the wild.

**How severe is CVE-2016-9311?** Medium severity, with a CVSS score of 5.9, published 13 January 2017.

**Which products and versions are affected?** NTP Project Ntpd before 4.2.8p9.

**Is there a fix for CVE-2016-9311?** A patch was published on 2016-11-21: Fixed in NTP 4.2.8p9 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-9311 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2016-9311?** Check whether you run Ntp or NTP Project Ntpd at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A NULL pointer dereference vulnerability exists in the trap service implementation of ntpd. When the trap service is enabled, a remote, unauthenticated attacker can send a specially crafted packet to trigger the dereference, causing the ntpd process to crash. This vulnerability is exploited via the network and requires the trap service to be active, which is not the default configuration in all environments. The issue is resolved in NTP version 4.2.8p9.

## Affected products

- NTP Project ntpd before 4.2.8p9
- Red Hat Enterprise Linux 6, 7

## Timeline

- 2016-11-21: disclosed: Initial public disclosure via NTP project bug 3119
- 2016-11-21: patched: Fixed in NTP 4.2.8p9
- 2017-01-13: advisory: NVD publication date

## References

- [http://nwtime.org/ntp428p9_release/](http://nwtime.org/ntp428p9_release/)
- [http://rhn.redhat.com/errata/RHSA-2017-0252.html](http://rhn.redhat.com/errata/RHSA-2017-0252.html)
- [http://support.ntp.org/bin/view/Main/NtpBug3119](http://support.ntp.org/bin/view/Main/NtpBug3119)
- [http://support.ntp.org/bin/view/Main/SecurityNotice](http://support.ntp.org/bin/view/Main/SecurityNotice)
- [http://www.securityfocus.com/bid/94444](http://www.securityfocus.com/bid/94444)
- [http://www.securitytracker.com/id/1037354](http://www.securitytracker.com/id/1037354)
- [https://bto.bluecoat.com/security-advisory/sa139](https://bto.bluecoat.com/security-advisory/sa139)

## Related threats

- [NTP ntpd denial of service in ctl_getitem](https://junglewise.ai/threats/cve-2016-2519-ntp-ntpd-denial-of-service-in-ctl-getitem)
- [NTP ntpq protocol replay attack vulnerability](https://junglewise.ai/threats/cve-2015-8140-ntp-ntpq-protocol-replay-attack-vulnerability)
- [NTP ntpq origin timestamp leak and peer impersonation](https://junglewise.ai/threats/cve-2015-8139-ntp-ntpq-origin-timestamp-leak-and-peer-impersonation)
- [NTP Project ntpd origin timestamp validation bypass](https://junglewise.ai/threats/cve-2015-8138-ntp-project-ntpd-origin-timestamp-validation-bypass)
- [NTP Project ntpd denial of service via reslist command](https://junglewise.ai/threats/cve-2015-7977-ntp-project-ntpd-denial-of-service-via-reslist-command)