CVE-2018-8956Network attack vector

Broadcast time synchronization disruption via spoofed NTP packets

Published May 6, 2020 · Updated Aug 5, 2024

Denial of service in ntpd in ntp 4.2.8p10 through 4.2.8p13 allows remote attackers to stop broadcast clients synchronizing via spoofed NTP packets. The daemon accepts forged mode 3 and mode 5 server-style packets that interfere with broadcast association state and block clock updates. Attackers must share the broadcast network or control a slave that captures required packets; the bounded impact is loss of time synchronization rather than data disclosure or modification.

CVSS severity5.3
Medium
EPSS probability3.07%
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 ntpd in ntp 4.2.8p10 through 4.2.8p13 allows remote attackers to stop broadcast clients synchronizing via spoofed NTP packets. The daemon accepts forged mode 3 and mode 5 server-style packets that interfere with broadcast association state and block clock updates. Attackers must share the broadcast network or control a slave that captures required packets; the bounded impact is loss of time synchronization rather than data disclosure or modification.

The record

CVE
CVE-2018-8956
Published
May 6, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T1498.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2024Record 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

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1498.001Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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