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
9.8EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 82%
  • Public exploit code is available (Metasploit, epss top5pct, epss high, public exploit)
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 9.8Exploit: Metasploit · epss top5pct · epss high · public exploitExposed: 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)
EG Risk
81(Track*)
EG Risk 81/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation82% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
82%
EPSS %ILE
100%
KEV
Not listed

Published

August 7, 2017

Last Modified

June 17, 2026

Advisory Details (9)

Auto-updated Aug 25, 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
generic
https://cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
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

CVE-2015-7871 - PSIRT.COM

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.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
ntp—1:4.2.8p4+dfsg-1—
Debian:6.0(1)
PackageVulnerable rangeFixed inDependents
ntp1:4.2.6.p2+dfsg-11:4.2.6.p2+dfsg-1+deb6u4—
Debian:7(1)
PackageVulnerable rangeFixed inDependents
ntp1:4.2.6.p5+dfsg-2 ... 1:4.2.6.p5+dfsg-2+deb7u5 (6 versions)1:4.2.6.p5+dfsg-2+deb7u6—
Debian:8(1)
PackageVulnerable rangeFixed inDependents
ntp1:4.2.6.p5+dfsg-71:4.2.6.p5+dfsg-7+deb8u1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

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 4× in last 7d / 11× 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. 2026-08-26 15:06 UTCOSV refresh
  2. 2026-08-26 14:41 UTCEPSS rescore
  3. 2026-08-25 13:44 UTCEPSS rescore
  4. 2026-08-21 23:44 UTCEPSS rescore
  5. 2026-08-19 16:59 UTCEPSS rescore
  6. 2026-08-18 13:43 UTCEPSS rescore
  7. 2026-08-16 02:09 UTCEPSS rescore
  8. 2026-08-15 01:25 UTCEPSS rescore
  9. 2026-08-12 13:46 UTCEPSS rescore
  10. 2026-08-10 04:09 UTCOSV refresh
  11. 2026-08-05 19:12 UTCEPSS rescore
  12. 2026-07-26 14:50 UTCEPSS rescore
  13. 2026-07-25 14:13 UTCEPSS rescore
  14. 2026-07-25 04:41 UTCOSV refresh
  15. 2026-07-24 14:13 UTCEPSS rescore
  16. 2026-07-23 14:14 UTCEPSS rescore
  17. 2026-07-23 01:19 UTCEG score recompute
  18. 2026-07-23 00:21 UTCEG score recompute
  19. 2026-07-22 21:59 UTCEG score recompute
  20. 2026-07-22 14:04 UTCEPSS rescore
  21. 2026-07-21 15:21 UTCEPSS rescore
  22. 2026-07-21 15:21 UTCEPSS rescore
  23. 2026-07-20 17:03 UTCEPSS rescore
  24. 2026-07-16 16:59 UTCEPSS rescore
  25. 2026-07-15 16:54 UTCEPSS rescore
Show 61 more
  1. 2026-07-15 16:54 UTCEPSS rescore
  2. 2026-07-13 22:26 UTCEPSS rescore
  3. 2026-07-13 22:26 UTCEPSS rescore
  4. 2026-07-09 19:05 UTCEPSS rescore
  5. 2026-07-09 19:05 UTCEPSS rescore
  6. 2026-07-07 23:27 UTCOSV refresh
  7. 2026-07-05 02:26 UTCEPSS rescore
  8. 2026-06-30 23:19 UTCEPSS rescore
  9. 2026-06-30 23:19 UTCEPSS rescore
  10. 2026-06-29 14:03 UTCEPSS rescore
  11. 2026-06-29 14:03 UTCEPSS rescore
  12. 2026-06-27 03:05 UTCEPSS rescore
  13. 2026-06-25 13:47 UTCEPSS rescore
  14. 2026-06-25 13:47 UTCEPSS rescore
  15. 2026-06-23 21:30 UTCEPSS rescore
  16. 2026-06-21 01:57 UTCEPSS rescore
  17. 2026-06-21 01:57 UTCEPSS rescore
  18. 2026-06-19 11:25 UTCOSV refresh
  19. 2026-06-16 17:50 UTCEPSS rescore
  20. 2026-06-16 17:50 UTCEPSS rescore
  21. 2026-06-15 17:45 UTCEPSS rescore
  22. 2026-06-14 23:14 UTCEPSS rescore
  23. 2026-06-12 23:09 UTCEPSS rescore
  24. 2026-06-12 23:09 UTCEPSS rescore
  25. 2026-06-10 22:15 UTCEPSS rescore
  26. 2026-06-06 13:45 UTCEPSS rescore
  27. 2026-06-05 22:44 UTCEPSS rescore
  28. 2026-06-05 06:08 UTCEPSS rescore
  29. 2026-06-05 06:08 UTCEPSS rescore
  30. 2026-05-31 00:14 UTCEPSS rescore
  31. 2026-05-30 19:53 UTCOSV refresh
  32. 2026-05-28 13:42 UTCEPSS rescore
  33. 2026-05-28 13:42 UTCEPSS rescore
  34. 2026-05-26 07:16 UTCEPSS rescore
  35. 2026-05-26 07:16 UTCEPSS rescore
  36. 2026-05-22 21:15 UTCEPSS rescore
  37. 2026-05-21 22:40 UTCEPSS rescore
  38. 2026-05-20 22:37 UTCEPSS rescore
  39. 2026-05-20 22:37 UTCEPSS rescore
  40. 2026-05-20 08:03 UTCVendor advisory
  41. 2026-05-20 08:03 UTCGHSA enrichment
  42. 2026-05-20 04:25 UTCVendor advisory
  43. 2026-05-20 04:25 UTCGHSA enrichment
  44. 2026-05-20 00:47 UTCVendor advisory
  45. 2026-05-20 00:47 UTCGHSA enrichment
  46. 2026-05-19 21:09 UTCVendor advisory
  47. 2026-05-19 21:09 UTCGHSA enrichment
  48. 2026-05-19 17:31 UTCVendor advisory
  49. 2026-05-19 17:31 UTCGHSA enrichment
  50. 2026-05-19 13:53 UTCVendor advisory
  51. 2026-05-19 13:53 UTCGHSA enrichment
  52. 2026-05-19 10:14 UTCVendor advisory
  53. 2026-05-19 10:14 UTCGHSA enrichment
  54. 2026-05-19 06:36 UTCVendor advisory
  55. 2026-05-19 06:35 UTCGHSA enrichment
  56. 2026-05-19 02:57 UTCVendor advisory
  57. 2026-05-19 02:57 UTCGHSA enrichment
  58. 2026-05-18 23:19 UTCEG score recompute
  59. 2026-05-18 23:19 UTCVendor advisory
  60. 2026-05-18 21:30 UTCEPSS rescore
  61. 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 ↗

Related CVEs(same vendor + same CWE)

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 June 17, 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 82% probability of exploitation in the next 30 days, which ranks it in the top 0.4% of all scored CVEs.
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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