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 verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High exploitation likelihood — EPSS 82%
  • Public exploit code is available (Metasploit)
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 9.8Exploit: MetasploitExposed services: Not assessed

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
9.8CRITICALmedium confidence
EG Risk
81
EG Risk 81/100

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 (value × EchelonGraph’s weight)
Severity98% × 45%
The EG Score, 9.8 of 10.
Exploitation82% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability30% × 15%
EchelonGraph's default before algorithm v3.4: CISA had not published Automatable for this CVE.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (EG-KEV: weaponized) · Automatable unknown (not published for this CVE) · Technical impact total (CVSS ≥ 9.0). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
82%
EPSS %ILE
99th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (EG-KEV: weaponized) · Automatable unknown (not published for this CVE) · Technical impact total (CVSS ≥ 9.0). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

Published

August 7, 2017

Last Modified

June 17, 2026

Advisory Details (9)

Auto-updated Oct 7, 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
redhatMentions a patch (unverified)

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

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
generic
http://www.securitytracker.com/id/1033951

Patch Availability(1)

Vendor / EcosystemFix (by version range) / 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 rangeFix by version rangeDependents
ntp—
  • every version up to 1:4.2.8p4+dfsg-1: fixed in 1:4.2.8p4+dfsg-1
—
Debian:6.0(1)
PackageVulnerable rangeFix by version rangeDependents
ntp1:4.2.6.p2+dfsg-1
  • every version up to 1:4.2.6.p2+dfsg-1+deb6u4: fixed in 1:4.2.6.p2+dfsg-1+deb6u4
—
Debian:7(1)
PackageVulnerable rangeFix by version rangeDependents
ntp1:4.2.6.p5+dfsg-2 ... 1:4.2.6.p5+dfsg-2+deb7u5 (6 versions)
  • every version up to 1:4.2.6.p5+dfsg-2+deb7u6: fixed in 1:4.2.6.p5+dfsg-2+deb7u6
—
Debian:8(1)
PackageVulnerable rangeFix by version rangeDependents
ntp1:4.2.6.p5+dfsg-7
  • every version up to 1:4.2.6.p5+dfsg-7+deb8u1: fixed in 1:4.2.6.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 3× in last 7d / 11× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 16 repeat rows among the latest 100 are merged into the row they repeat.

  1. 2026-10-09 20:01 UTCEPSS rescoreEPSS 82% · 99th percentile
  2. 2026-10-07 23:40 UTCEPSS rescoreEPSS 82% · 99th percentile
  3. 2026-10-05 17:38 UTCEPSS rescoreEPSS 82% · 99th percentile
  4. 2026-10-03 23:49 UTCOSV refresh
  5. 2026-09-30 09:07 UTCEG score recompute
  6. 2026-09-27 13:40 UTCEPSS rescoreEPSS 82% · 99th percentile
  7. 2026-09-26 15:53 UTCEPSS rescoreEPSS 82% · 99th percentile
  8. 2026-09-18 19:22 UTCEPSS rescoreEPSS 82% · 99th percentile
  9. 2026-09-17 19:21 UTCEPSS rescoreEPSS 82% · 99th percentile
  10. 2026-09-15 03:05 UTCEPSS rescoreEPSS 82% · 99th percentile
  11. 2026-09-14 14:14 UTCOSV refresh
  12. 2026-09-10 09:26 UTCEPSS rescoreEPSS 82% · 99th percentile
  13. 2026-09-06 13:42 UTCEPSS rescoreEPSS 82% · 99th percentile
  14. 2026-08-26 15:06 UTCOSV refresh
  15. 2026-08-26 14:41 UTCEPSS rescoreEPSS 82% · 99th percentile
  16. 2026-08-25 13:44 UTCEPSS rescoreEPSS 82% · 99th percentile
  17. 2026-08-21 23:44 UTCEPSS rescoreEPSS 82% · 99th percentile
  18. 2026-08-19 16:59 UTCEPSS rescoreEPSS 82% · 99th percentile
  19. 2026-08-18 13:43 UTCEPSS rescoreEPSS 82% · 99th percentile
  20. 2026-08-16 02:09 UTCEPSS rescoreEPSS 82% · 99th percentile
  21. 2026-08-15 01:25 UTCEPSS rescoreEPSS 82% · 99th percentile
  22. 2026-08-12 13:46 UTCEPSS rescoreEPSS 82% · 99th percentile
  23. 2026-08-10 04:09 UTCOSV refresh
  24. 2026-08-05 19:12 UTCEPSS rescoreEPSS 82% · 99th percentile
  25. 2026-07-26 14:50 UTCEPSS rescoreEPSS 82% · 99th percentile
Show 59 more
  1. 2026-07-25 14:13 UTCEPSS rescoreEPSS 82% · 99th percentile
  2. 2026-07-25 04:41 UTCOSV refresh
  3. 2026-07-24 14:13 UTCEPSS rescoreEPSS 82% · 99th percentile
  4. 2026-07-23 14:14 UTCEPSS rescoreEPSS 82% · 99th percentile
  5. 2026-07-23 01:19 UTCEG score recompute
  6. 2026-07-23 00:21 UTCEG score recompute
  7. 2026-07-22 21:59 UTCEG score recompute
  8. 2026-07-22 14:04 UTCEPSS rescoreEPSS 82% · 99th percentile
  9. 2026-07-21 15:21 UTCEPSS rescoreEPSS 82% · 99th percentile
  10. 2026-07-20 17:03 UTCEPSS rescoreEPSS 82% · 99th percentile
  11. 2026-07-16 16:59 UTCEPSS rescoreEPSS 82% · 99th percentile
  12. 2026-07-15 16:54 UTCEPSS rescoreEPSS 82% · 99th percentile
  13. 2026-07-13 22:26 UTCEPSS rescoreEPSS 82% · 99th percentile
  14. 2026-07-09 19:05 UTCEPSS rescoreEPSS 82% · 99th percentile
  15. 2026-07-07 23:27 UTCOSV refresh
  16. 2026-07-05 02:26 UTCEPSS rescoreEPSS 82% · 99th percentile
  17. 2026-06-30 23:19 UTCEPSS rescoreEPSS 82% · 99th percentile
  18. 2026-06-29 14:03 UTCEPSS rescoreEPSS 82% · 99th percentile
  19. 2026-06-27 03:05 UTCEPSS rescoreEPSS 82% · 99th percentile
  20. 2026-06-25 13:47 UTCEPSS rescoreEPSS 82% · 99th percentile
  21. 2026-06-23 21:30 UTCEPSS rescoreEPSS 82% · 99th percentile
  22. 2026-06-21 01:57 UTCEPSS rescoreEPSS 82% · 99th percentile
  23. 2026-06-19 11:25 UTCOSV refresh
  24. 2026-06-16 17:50 UTCEPSS rescoreEPSS 82% · 99th percentile
  25. 2026-06-15 17:45 UTCEPSS rescoreEPSS 82% · 99th percentile
  26. 2026-06-14 23:14 UTCEPSS rescoreEPSS 84% · 99th percentile
  27. 2026-06-12 23:09 UTCEPSS rescoreEPSS 84% · 99th percentile
  28. 2026-06-10 22:15 UTCEPSS rescoreEPSS 84% · 99th percentile
  29. 2026-06-06 13:45 UTCEPSS rescoreEPSS 84% · 99th percentile
  30. 2026-06-05 22:44 UTCEPSS rescoreEPSS 84% · 99th percentile
  31. 2026-06-05 06:08 UTCEPSS rescoreEPSS 84% · 99th percentile
  32. 2026-05-31 00:14 UTCEPSS rescoreEPSS 84% · 99th percentile
  33. 2026-05-30 19:53 UTCOSV refresh
  34. 2026-05-28 13:42 UTCEPSS rescoreEPSS 84% · 99th percentile
  35. 2026-05-26 07:16 UTCEPSS rescoreEPSS 84% · 99th percentile
  36. 2026-05-22 21:15 UTCEPSS rescoreEPSS 84% · 99th percentile
  37. 2026-05-21 22:40 UTCEPSS rescoreEPSS 84% · 99th percentile
  38. 2026-05-20 22:37 UTCEPSS rescoreEPSS 80% · 99th percentile
  39. 2026-05-20 08:03 UTCVendor advisory
  40. 2026-05-20 08:03 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  41. 2026-05-20 04:25 UTCVendor advisory
  42. 2026-05-20 04:25 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  43. 2026-05-20 00:47 UTCVendor advisory
  44. 2026-05-20 00:47 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  45. 2026-05-19 21:09 UTCVendor advisory
  46. 2026-05-19 21:09 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  47. 2026-05-19 17:31 UTCVendor advisory
  48. 2026-05-19 17:31 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  49. 2026-05-19 13:53 UTCVendor advisory
  50. 2026-05-19 13:53 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  51. 2026-05-19 10:14 UTCVendor advisory
  52. 2026-05-19 10:14 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  53. 2026-05-19 06:36 UTCVendor advisory
  54. 2026-05-19 06:35 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  55. 2026-05-19 02:57 UTCVendor advisory
  56. 2026-05-19 02:57 UTCGHSA enrichmentGHSA-mxc3-mjx4-gjc9 · GitHub severity CRITICAL · GitHub CVSS 9.8
  57. 2026-05-18 23:19 UTCEG score recompute
  58. 2026-05-18 23:19 UTCVendor advisory
  59. 2026-05-18 21:30 UTCEPSS rescoreEPSS 80% · 99th percentile

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 Metasploit module). Defenders should treat patch urgency accordingly.

  • Metasploitauxiliary/scanner/ntp/ntp_nak_to_the_future✓ verified
    Published Dec 24, 2015

    NTP "NAK to the Future"

    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2015-7871?
CVE-2015-7871 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2015-7871 published?
The CVE record for CVE-2015-7871 was published on August 7, 2017. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of June 17, 2026; the record at its source may have been updated since.
Is CVE-2015-7871 actively exploited?
CVE-2015-7871 is not currently on CISA's Known Exploited Vulnerabilities catalog. EchelonGraph's EG-KEV model places it in Tier 2 (Weaponized), which is not evidence of exploitation: a Metasploit module exists for it. EchelonGraph does not test whether exploit code works. FIRST EPSS estimates a 82% probability of exploitation in the next 30 days (99th percentile of EPSS-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?
A fix for CVE-2015-7871 is available: update to the fixed version the vendor names in its advisory.

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