CVE-2016-1547

What it is

An off-path attacker can cause a preemptible client association to be demobilized in NTP 4.2.8p4 and earlier and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92 by sending a crypto NAK packet to a victim client with a spoofed source address of an existing associated peer. This is true even if authentication is enabled.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

5.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2017-01-06 21:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:42 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 5.1% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2017-01-06 21:59 UTC

Last modified

2026-06-17 00:42 UTC

Exploit probability

5.1% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Ntp ≤ 4.2.8

Attack profile CVSS 3.0 · 5.3

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-1547.md and follow it. Check whether this project is affected by CVE-2016-1547. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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