CVE-2015-7871

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-13. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Weaponized
9.8
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 82%
CISA-KEV: Not listedEPSS: 82%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
99.6%
KEV
Not listed

Published

August 7, 2017

Last Modified

May 13, 2026

Advisory Details (8)

Auto-updated May 15, 2026
Patch available. Sources: redhat.
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20171004-0001/
generic

NTP: Multiple vulnerabilities (GLSA 201607-15) — Gentoo security

https://security.gentoo.org/glsa/201607-15
generic

Xen: Multiple vulnerabilities (GLSA 201604-03) — Gentoo security

https://security.gentoo.org/glsa/201604-03
generic
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05270839
redhat Patch Available

1274265 – (CVE-2015-7871) CVE-2015-7871 ntp: crypto-NAK symmetric association authentication bypass vulnerability

Affected: Red Hat Enterprise Linux 5, 6, and 7.

https://bugzilla.redhat.com/show_bug.cgi?id=1274265
generic
http://www.securitytracker.com/id/1033951
generic
http://www.securityfocus.com/bid/77287
generic

[SECURITY] [DSA 3388-1] ntp security update

http://www.debian.org/security/2015/dsa-3388

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuntp (1:4.2.6.p3+dfsg-1ubuntu3.6) @ precise2026-05-20ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 3× in last 7d / 19× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-05 02:26 UTCEPSS rescore
  2. 2026-06-30 23:19 UTCEPSS rescore
  3. 2026-06-30 23:19 UTCEPSS rescore
  4. 2026-06-29 14:03 UTCEPSS rescore
  5. 2026-06-29 14:03 UTCEPSS rescore
  6. 2026-06-27 03:05 UTCEPSS rescore
  7. 2026-06-25 13:47 UTCEPSS rescore
  8. 2026-06-25 13:47 UTCEPSS rescore
  9. 2026-06-23 21:30 UTCEPSS rescore
  10. 2026-06-21 01:57 UTCEPSS rescore
  11. 2026-06-21 01:57 UTCEPSS rescore
  12. 2026-06-19 11:25 UTCOSV refresh
  13. 2026-06-16 17:50 UTCEPSS rescore
  14. 2026-06-16 17:50 UTCEPSS rescore
  15. 2026-06-15 17:45 UTCEPSS rescore
  16. 2026-06-14 23:14 UTCEPSS rescore
  17. 2026-06-12 23:09 UTCEPSS rescore
  18. 2026-06-12 23:09 UTCEPSS rescore
  19. 2026-06-10 22:15 UTCEPSS rescore
  20. 2026-06-06 13:45 UTCEPSS rescore
  21. 2026-06-05 22:44 UTCEPSS rescore
  22. 2026-06-05 06:08 UTCEPSS rescore
  23. 2026-06-05 06:08 UTCEPSS rescore
  24. 2026-05-31 00:14 UTCEPSS rescore
  25. 2026-05-30 19:53 UTCOSV refresh
Show 39 more
  1. 2026-05-28 13:42 UTCEPSS rescore
  2. 2026-05-28 13:42 UTCEPSS rescore
  3. 2026-05-26 07:16 UTCEPSS rescore
  4. 2026-05-26 07:16 UTCEPSS rescore
  5. 2026-05-22 21:15 UTCEPSS rescore
  6. 2026-05-21 22:40 UTCEPSS rescore
  7. 2026-05-20 22:37 UTCEPSS rescore
  8. 2026-05-20 22:37 UTCEPSS rescore
  9. 2026-05-20 08:03 UTCEG score recompute
  10. 2026-05-20 08:03 UTCVendor advisory
  11. 2026-05-20 08:03 UTCGHSA enrichment
  12. 2026-05-20 04:25 UTCEG score recompute
  13. 2026-05-20 04:25 UTCVendor advisory
  14. 2026-05-20 04:25 UTCGHSA enrichment
  15. 2026-05-20 00:47 UTCEG score recompute
  16. 2026-05-20 00:47 UTCVendor advisory
  17. 2026-05-20 00:47 UTCGHSA enrichment
  18. 2026-05-19 21:09 UTCEG score recompute
  19. 2026-05-19 21:09 UTCVendor advisory
  20. 2026-05-19 21:09 UTCGHSA enrichment
  21. 2026-05-19 17:31 UTCEG score recompute
  22. 2026-05-19 17:31 UTCVendor advisory
  23. 2026-05-19 17:31 UTCGHSA enrichment
  24. 2026-05-19 13:53 UTCEG score recompute
  25. 2026-05-19 13:53 UTCVendor advisory
  26. 2026-05-19 13:53 UTCGHSA enrichment
  27. 2026-05-19 10:14 UTCEG score recompute
  28. 2026-05-19 10:14 UTCVendor advisory
  29. 2026-05-19 10:14 UTCGHSA enrichment
  30. 2026-05-19 06:36 UTCEG score recompute
  31. 2026-05-19 06:36 UTCVendor advisory
  32. 2026-05-19 06:35 UTCGHSA enrichment
  33. 2026-05-19 02:57 UTCEG score recompute
  34. 2026-05-19 02:57 UTCVendor advisory
  35. 2026-05-19 02:57 UTCGHSA enrichment
  36. 2026-05-18 23:19 UTCEG score recompute
  37. 2026-05-18 23:19 UTCVendor advisory
  38. 2026-05-18 21:30 UTCEPSS rescore
  39. 2026-05-18 21:30 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Metasploit module). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Metasploitauxiliary/scanner/ntp/ntp_nak_to_the_future✓ verified
    First seen Jan 1, 2015

    NTP "NAK to the Future"

    Open source ↗

Frequently asked(5)

What is CVE-2015-7871?
CVE-2015-7871 is a critical vulnerability published on August 7, 2017. Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.
When was CVE-2015-7871 disclosed?
CVE-2015-7871 was first published in the National Vulnerability Database on August 7, 2017, with the most recent update on May 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2015-7871 actively exploited?
CVE-2015-7871 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2015-7871?
CVE-2015-7871 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2015-7871?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2015-7871, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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