# CVE-2016-1549: Business logic in NTP

> An authenticated attacker can manipulate the NTP clock selection algorithm to modify a victim's system time.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jan 2017
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-1549, GHSA-r89j-r995-h68w, UBUNTU-CVE-2016-1549

## What is CVE-2016-1549?

CVE-2016-1549 is a medium-severity vulnerability in Ntp Ntp, published on 6 Jan 2017. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A malicious authenticated peer can create arbitrarily-many ephemeral associations in order to win the clock selection algorithm in ntpd in NTP 4.2.8p4 and earlier and NTPsec 3e160db8dc248a0bcb053b56a80167dc742d2b74 and a5fb34b9cc89b92a8fef2f459004865c93bb7f92 and modify a victim's clock.

Weakness: CWE-19

## Which versions are affected by CVE-2016-1549?

It affects 1 product.


Products: Ntp Ntp.

## How do I fix CVE-2016-1549?

Upgrade to a fixed version.

## Is CVE-2016-1549 being exploited?

There is no known exploitation of CVE-2016-1549 in the wild and no public exploit code.

## Other vulnerabilities in Ntp Ntp

- [CVE-2018-12327](https://insights.sbomify.com/CVE-2018-12327/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-6460](https://insights.sbomify.com/CVE-2017-6460/): Memory corruption in n/a (high 8.8)
- [CVE-2019-11331](https://insights.sbomify.com/CVE-2019-11331/): Other in n/a (high 8.1)
- [CVE-2017-6451](https://insights.sbomify.com/CVE-2017-6451/): Memory corruption in n/a (high 7.8)
- [CVE-2017-6452](https://insights.sbomify.com/CVE-2017-6452/): Memory corruption in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-1549 and fix it if it is affected.

What it is: CVE-2016-1549 is a medium-severity vulnerability in Ntp Ntp, published on 6 Jan 2017. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2016-1549 in the wild and no public exploit code.

Affected product: Ntp Ntp. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2016-1549/ (Markdown: https://insights.sbomify.com/CVE-2016-1549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-1549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-1549
- OSV: https://osv.dev/vulnerability/CVE-2016-1549

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-1549/
Summaries are generated and may contain mistakes; the official description above is the record.