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PatchSiren cyber security CVE debrief

CVE-2016-7431 Ntp CVE debrief

CVE-2016-7431 is a medium-severity NTP flaw affecting versions before 4.2.8p9. According to the NVD record, a remote attacker could bypass the origin timestamp protection mechanism by using an origin timestamp of zero. The record also notes that this issue exists as a regression related to CVE-2015-8138. The practical security impact is limited to integrity, but it is reachable over the network without privileges or user interaction.

Vendor
Ntp
Product
Unknown
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2021-06-08
Original CVE updated
2025-05-06
Advisory published
2021-06-08
Advisory updated
2025-05-06

Who should care

Administrators and vendors running affected NTP deployments, especially systems pinned to NTP 4.2.8p8 or earlier. Security teams should also care if NTP is embedded in appliances or infrastructure products that consume upstream NTP fixes slowly.

Technical summary

The NVD description says the flaw allows remote attackers to bypass origin timestamp protection by supplying an origin timestamp of zero. NVD maps the affected CPE to ntp:4.2.8:p8 and earlier versions in the same line, and classifies the weakness as CWE-20 (improper input validation). The CVSS v3.0 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N, which aligns with a network-reachable integrity issue rather than confidentiality or availability impact. The description explicitly states this is a regression from CVE-2015-8138.

Defensive priority

Medium. Patch promptly if you operate affected NTP versions, but this is not listed as a KEV item in the supplied corpus and does not indicate availability impact.

Recommended defensive actions

  • Upgrade NTP to 4.2.8p9 or a later fixed release.
  • Confirm whether any appliances, OS packages, or embedded products bundle affected NTP versions, including 4.2.8p8.
  • Follow vendor and distribution advisories linked from the NVD record for platform-specific remediation steps.
  • Validate that compensating controls do not rely solely on origin timestamp protection for trust decisions.
  • Inventory time-synchronization services and prioritize externally exposed or widely reused infrastructure images first.

Evidence notes

This debrief is based only on the supplied NVD record and referenced official/vendor links. The NVD description states: NTP before 4.2.8p9 allows remote attackers to bypass origin timestamp protection via an origin timestamp of zero, and notes the issue exists because of a CVE-2015-8138 regression. NVD also provides the CVSS vector CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N, CWE-20, and an affected CPE entry for ntp 4.2.8p8. No exploit details or unverified impact claims are included.

Sources and references

Verified primary and authoritative sources

  • CVE-2016-7431 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2016-7431

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2016-7431 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2016-7431

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.