CVE-2026-66305

HIGHPre-NVD 7.17.1—
EchelonGraph scoreHIGH confidence

Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2026-09-08. the CNA's CVSS baseline 7.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
Trending — 4 sources updated this week
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.1Exploit: None knownExposed: 0

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

Use of client-side authentication in Skype for Business allows an authorized attacker to perform spoofing over a network.

CVSS v3
7.1
EG Score
7.1(high)
EG Risk
32(Track)
EG Risk 32/100SSVC: 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
Severity71% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
22%
KEV
Not listed

Published

September 8, 2026

Last Modified

September 18, 2026

Advisory Details (1)

Auto-updated Sep 8, 2026
Patch available. Sources: microsoft.
microsoft Patch Available

Security Update Guide - Microsoft Security Response Center

Security Update Guide - Microsoft Security Response Center. Patch available via Microsoft Security Update

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66305

Vendor Advisories for CVE-2026-66305(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 49× in last 7d / 86× 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. 2026-09-19 09:47 UTCVendor advisory
  2. 2026-09-19 09:47 UTCGHSA enrichment
  3. 2026-09-18 20:46 UTCEG score recompute
  4. 2026-09-18 20:46 UTCVendor advisory
  5. 2026-09-18 20:46 UTCGHSA enrichment
  6. 2026-09-18 19:28 UTCEPSS rescore
  7. 2026-09-18 13:50 UTCVendor advisory
  8. 2026-09-18 13:50 UTCGHSA enrichment
  9. 2026-09-18 11:43 UTCVendor advisory
  10. 2026-09-18 11:43 UTCGHSA enrichment
  11. 2026-09-17 23:05 UTCVendor advisory
  12. 2026-09-17 23:05 UTCGHSA enrichment
  13. 2026-09-17 19:55 UTCEG score recompute
  14. 2026-09-17 19:55 UTCVendor advisory
  15. 2026-09-17 19:54 UTCGHSA enrichment
  16. 2026-09-17 10:39 UTCVendor advisory
  17. 2026-09-17 10:39 UTCGHSA enrichment
  18. 2026-09-16 22:00 UTCEG score recompute
  19. 2026-09-16 22:00 UTCVendor advisory
  20. 2026-09-16 22:00 UTCGHSA enrichment
  21. 2026-09-16 19:37 UTCEG score recompute
  22. 2026-09-16 19:37 UTCVendor advisory
  23. 2026-09-16 19:37 UTCGHSA enrichment
  24. 2026-09-16 14:08 UTCEPSS rescore
  25. 2026-09-16 11:26 UTCEG score recompute
Show 61 more
  1. 2026-09-16 11:26 UTCVendor advisory
  2. 2026-09-16 11:26 UTCGHSA enrichment
  3. 2026-09-16 05:15 UTCEPSS rescore
  4. 2026-09-15 22:46 UTCVendor advisory
  5. 2026-09-15 22:46 UTCGHSA enrichment
  6. 2026-09-15 17:40 UTCVendor advisory
  7. 2026-09-15 17:40 UTCGHSA enrichment
  8. 2026-09-15 11:33 UTCEG score recompute
  9. 2026-09-15 11:33 UTCVendor advisory
  10. 2026-09-15 11:33 UTCGHSA enrichment
  11. 2026-09-14 22:55 UTCVendor advisory
  12. 2026-09-14 22:55 UTCGHSA enrichment
  13. 2026-09-14 17:21 UTCVendor advisory
  14. 2026-09-14 17:21 UTCGHSA enrichment
  15. 2026-09-14 13:40 UTCVendor advisory
  16. 2026-09-14 13:40 UTCGHSA enrichment
  17. 2026-09-14 00:57 UTCEG score recompute
  18. 2026-09-14 00:57 UTCVendor advisory
  19. 2026-09-14 00:57 UTCGHSA enrichment
  20. 2026-09-13 12:20 UTCVendor advisory
  21. 2026-09-13 12:20 UTCGHSA enrichment
  22. 2026-09-12 23:43 UTCEG score recompute
  23. 2026-09-12 23:43 UTCVendor advisory
  24. 2026-09-12 23:43 UTCGHSA enrichment
  25. 2026-09-12 11:05 UTCVendor advisory
  26. 2026-09-12 11:05 UTCGHSA enrichment
  27. 2026-09-11 22:27 UTCVendor advisory
  28. 2026-09-11 22:27 UTCGHSA enrichment
  29. 2026-09-11 19:44 UTCVendor advisory
  30. 2026-09-11 19:44 UTCGHSA enrichment
  31. 2026-09-11 16:49 UTCEG score recompute
  32. 2026-09-11 16:49 UTCVendor advisory
  33. 2026-09-11 16:49 UTCGHSA enrichment
  34. 2026-09-11 14:53 UTCEPSS rescore
  35. 2026-09-11 11:59 UTCEG score recompute
  36. 2026-09-11 11:59 UTCGHSA enrichment
  37. 2026-09-11 09:37 UTCEPSS rescore
  38. 2026-09-10 23:21 UTCGHSA enrichment
  39. 2026-09-10 22:48 UTCGHSA enrichment
  40. 2026-09-10 10:10 UTCEG score recompute
  41. 2026-09-10 10:10 UTCGHSA enrichment
  42. 2026-09-09 21:33 UTCVendor advisory
  43. 2026-09-09 21:32 UTCGHSA enrichment
  44. 2026-09-09 19:46 UTCEG score recompute
  45. 2026-09-09 19:46 UTCVendor advisory
  46. 2026-09-09 19:46 UTCGHSA enrichment
  47. 2026-09-09 17:31 UTCEG score recompute
  48. 2026-09-09 17:31 UTCVendor advisory
  49. 2026-09-09 17:31 UTCGHSA enrichment
  50. 2026-09-09 16:47 UTCEG score recompute
  51. 2026-09-09 16:47 UTCVendor advisory
  52. 2026-09-09 16:47 UTCGHSA enrichment
  53. 2026-09-09 12:21 UTCVendor advisory
  54. 2026-09-09 12:21 UTCGHSA enrichment
  55. 2026-09-08 23:43 UTCEG score recompute
  56. 2026-09-08 23:43 UTCVendor advisory
  57. 2026-09-08 23:43 UTCGHSA enrichment
  58. 2026-09-08 19:32 UTCEG score recompute
  59. 2026-09-08 18:41 UTCEG score recompute
  60. 2026-09-08 18:41 UTCVendor advisory
  61. 2026-09-08 18:41 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-66305?
CVE-2026-66305 is a high vulnerability published on September 8, 2026. Use of client-side authentication in Skype for Business allows an authorized attacker to perform spoofing over a network.
When was CVE-2026-66305 disclosed?
CVE-2026-66305 was first published in the National Vulnerability Database on September 8, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66305 actively exploited?
CVE-2026-66305 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 77.6% of all scored CVEs.
What is the CVSS score of CVE-2026-66305?
CVE-2026-66305 has a CVSS v4.0 base score of 7.1 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-66305?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66305, 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

Explore the affected products and dependency analysis for CVE-2026-66305

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