# CVE-2016-9312: NTP Project ntpd denial of service via large UDP packet on Windows

Source: https://junglewise.ai/threats/cve-2016-9312-ntp-project-ntpd-denial-of-service-via-large-udp-packet-on-windows  
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-2016-9312 · Severity: high · CVSS 7.5 · Published 2017-01-13

A vulnerability in the Network Time Protocol daemon (ntpd) on Windows systems allows a remote attacker to crash the service. This component is responsible for synchronizing the system clock across a network. If exploited, the time-keeping service will stop functioning, which can disrupt scheduled tasks, security logging, and authentication protocols that rely on accurate time.

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

## Quick answers

**Is CVE-2016-9312 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9312 being exploited in the wild.

**How severe is CVE-2016-9312?** High severity, with a CVSS score of 7.5, published 13 January 2017.

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

**Is there a fix for CVE-2016-9312?** A patch was published on 2016-11-21: NTP 4.2.8p9 released to address the issue Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-9312 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2016-9312?** Check whether you run Microsoft Windows, 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 resource management error (CWE-410/CWE-399) exists in the Windows implementation of ntpd. A remote, unauthenticated attacker can send a specially crafted, oversized UDP packet to the NTP port (typically 123/UDP). Upon receipt of this 'too big' packet, the ntpd process fails to handle the input correctly and terminates, resulting in a denial of service. This issue is specific to the Windows port of ntpd and was addressed in version 4.2.8p9.

## Affected products

- NTP Project ntpd before 4.2.8p9
- Microsoft Windows

## Timeline

- 2016-11-21: advisory: Initial release of CERT/CC vulnerability note
- 2016-11-21: patched: NTP 4.2.8p9 released to address the issue
- 2017-01-13: disclosed: NVD publication date

## References

- [http://nwtime.org/ntp428p9_release/](http://nwtime.org/ntp428p9_release/)
- [http://support.ntp.org/bin/view/Main/NtpBug3110](http://support.ntp.org/bin/view/Main/NtpBug3110)
- [http://support.ntp.org/bin/view/Main/SecurityNotice](http://support.ntp.org/bin/view/Main/SecurityNotice)
- [http://www.securityfocus.com/bid/94450](http://www.securityfocus.com/bid/94450)
- [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)
- [https://www.kb.cert.org/vuls/id/633847](https://www.kb.cert.org/vuls/id/633847)

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