CVE-2025-66491

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 87% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
27(Track)
EG Risk 27/100SSVC: 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
Severity59% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

Published

December 9, 2025

Last Modified

June 17, 2026

References (3)

Affected Packages

(3 across 1 ecosystem)
Go(3)
PackageVulnerable rangeFixed inDependents
github.com/traefik/traefik———
github.com/traefik/traefik/v2———
github.com/traefik/traefik/v3—3.6.3—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 28× 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.

Showing the most recent 100 of 146 total refreshes for this CVE.

  1. 2026-09-19 15:42 UTCEPSS rescore
  2. 2026-09-18 19:27 UTCEPSS rescore
  3. 2026-09-17 19:30 UTCEPSS rescore
  4. 2026-09-16 14:07 UTCEPSS rescore
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  8. 2026-09-12 06:40 UTCOSV refresh
  9. 2026-09-11 14:52 UTCEPSS rescore
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  20. 2026-08-28 21:40 UTCEPSS rescore
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  23. 2026-08-25 13:48 UTCEPSS rescore
  24. 2026-08-24 14:16 UTCEPSS rescore
  25. 2026-08-24 12:00 UTCOSV refresh
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  1. 2026-08-23 00:18 UTCEPSS rescore
  2. 2026-08-21 23:48 UTCEPSS rescore
  3. 2026-08-20 22:55 UTCEPSS rescore
  4. 2026-08-19 17:03 UTCEPSS rescore
  5. 2026-08-17 13:46 UTCEPSS rescore
  6. 2026-08-16 14:55 UTCEPSS rescore
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  8. 2026-08-15 01:30 UTCEPSS rescore
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  10. 2026-08-13 21:59 UTCEPSS rescore
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  12. 2026-08-11 13:42 UTCEPSS rescore
  13. 2026-08-10 23:59 UTCEPSS rescore
  14. 2026-08-09 13:46 UTCEPSS rescore
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  16. 2026-08-08 16:36 UTCEPSS rescore
  17. 2026-08-08 08:04 UTCEG score recompute
  18. 2026-08-07 16:26 UTCEPSS rescore
  19. 2026-08-06 13:46 UTCEPSS rescore
  20. 2026-08-05 19:17 UTCEPSS rescore
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  22. 2026-08-04 15:09 UTCEPSS rescore
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  25. 2026-08-02 02:26 UTCEPSS rescore
  26. 2026-08-01 04:15 UTCEPSS rescore
  27. 2026-07-30 16:27 UTCEPSS rescore
  28. 2026-07-30 01:30 UTCEPSS rescore
  29. 2026-07-28 15:35 UTCEPSS rescore
  30. 2026-07-27 14:12 UTCEPSS rescore
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  36. 2026-07-23 14:18 UTCEPSS rescore
  37. 2026-07-23 14:18 UTCEPSS rescore
  38. 2026-07-23 13:19 UTCOSV refresh
  39. 2026-07-23 03:01 UTCEG score recompute
  40. 2026-07-22 14:08 UTCEPSS rescore
  41. 2026-07-21 15:24 UTCEPSS rescore
  42. 2026-07-20 17:08 UTCEPSS rescore
  43. 2026-07-19 14:30 UTCEPSS rescore
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  45. 2026-07-19 02:28 UTCEPSS rescore
  46. 2026-07-18 10:04 UTCEPSS rescore
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  48. 2026-07-16 17:02 UTCEPSS rescore
  49. 2026-07-15 16:57 UTCEPSS rescore
  50. 2026-07-15 16:57 UTCEPSS rescore
  51. 2026-07-15 01:59 UTCEPSS rescore
  52. 2026-07-15 01:59 UTCEPSS rescore
  53. 2026-07-13 22:29 UTCEPSS rescore
  54. 2026-07-13 06:12 UTCEPSS rescore
  55. 2026-07-12 05:46 UTCEPSS rescore
  56. 2026-07-11 08:27 UTCEPSS rescore
  57. 2026-07-09 19:09 UTCEPSS rescore
  58. 2026-07-08 15:15 UTCEPSS rescore
  59. 2026-07-07 13:46 UTCEPSS rescore
  60. 2026-07-06 16:27 UTCEPSS rescore
  61. 2026-07-06 16:27 UTCEPSS rescore
  62. 2026-07-06 08:11 UTCOSV refresh
  63. 2026-07-06 02:23 UTCEPSS rescore
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  65. 2026-07-05 02:30 UTCEPSS rescore
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  67. 2026-07-04 06:31 UTCEPSS rescore
  68. 2026-07-04 06:30 UTCEPSS rescore
  69. 2026-07-01 15:06 UTCEPSS rescore
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  71. 2026-06-30 23:22 UTCEPSS rescore
  72. 2026-06-29 14:06 UTCEPSS rescore
  73. 2026-06-29 14:06 UTCEPSS rescore
  74. 2026-06-28 14:07 UTCEPSS rescore
  75. 2026-06-28 14:07 UTCEPSS rescore

Frequently asked(5)

What is CVE-2025-66491?
CVE-2025-66491 is a medium vulnerability published on December 9, 2025. Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables…
When was CVE-2025-66491 disclosed?
CVE-2025-66491 was first published in the National Vulnerability Database on December 9, 2025, 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-2025-66491 actively exploited?
CVE-2025-66491 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 87.1% of all scored CVEs.
What is the CVSS score of CVE-2025-66491?
CVE-2025-66491 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2025-66491?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-66491, 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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