CVE-2020-11868Network attack vector

Synchronization denial via unvalidated origin timestamp

Published Apr 17, 2020 · Updated May 5, 2025

Denial of service in NTP ntpd before 4.2.8p14 or 4.3.x before 4.3.100 allows remote attackers to block time synchronization. The receive path reschedules client transmissions for a spoofed server-mode packet even when its origin timestamp does not match a valid request. An off-path attacker must spoof the configured server source address against a client using unauthenticated time sources, preventing synchronization without crashing ntpd.

CVSS severity7.5
High
EPSS probability2.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in NTP ntpd before 4.2.8p14 or 4.3.x before 4.3.100 allows remote attackers to block time synchronization. The receive path reschedules client transmissions for a spoofed server-mode packet even when its origin timestamp does not match a valid request. An off-path attacker must spoof the configured server source address against a client using unauthenticated time sources, preventing synchronization without crashing ntpd.

The record

CVE
CVE-2020-11868
Published
Apr 17, 2020
Updated
May 5, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-346, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 17, 2020CVE publishedPublication date reported by the CVE source.
  2. May 5, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.9IBMCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-346Origin Validation Error
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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