CVE-2026-66303

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-09-08. the CNA's CVSS baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 6.5Exploit: None knownExposed: 0

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

Null pointer dereference in Skype for Business allows an authorized attacker to deny service over a network.

CVSS v3
6.5
EG Score
6.5(high)
EG Risk
30(Track)
EG Risk 30/100SSVC: 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
Severity65% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
65%
KEV
Not listed

Published

September 8, 2026

Last Modified

September 24, 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-2026-66303

Vendor Advisories for CVE-2026-66303(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 36× in last 7d / 93× 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. 2026-09-24 22:37 UTCVendor advisory
  2. 2026-09-24 22:37 UTCGHSA enrichment
  3. 2026-09-24 20:47 UTCVendor advisory
  4. 2026-09-24 20:47 UTCGHSA enrichment
  5. 2026-09-24 17:32 UTCEG score recompute
  6. 2026-09-24 17:32 UTCVendor advisory
  7. 2026-09-24 17:32 UTCGHSA enrichment
  8. 2026-09-23 22:52 UTCVendor advisory
  9. 2026-09-23 22:51 UTCGHSA enrichment
  10. 2026-09-23 18:29 UTCEG score recompute
  11. 2026-09-23 18:29 UTCVendor advisory
  12. 2026-09-23 18:29 UTCGHSA enrichment
  13. 2026-09-23 17:54 UTCEPSS rescore
  14. 2026-09-23 12:53 UTCEG score recompute
  15. 2026-09-23 12:53 UTCVendor advisory
  16. 2026-09-23 12:53 UTCGHSA enrichment
  17. 2026-09-22 14:40 UTCEG score recompute
  18. 2026-09-22 14:40 UTCVendor advisory
  19. 2026-09-22 14:40 UTCGHSA enrichment
  20. 2026-09-21 16:27 UTCVendor advisory
  21. 2026-09-21 16:27 UTCGHSA enrichment
  22. 2026-09-21 15:49 UTCEG score recompute
  23. 2026-09-21 15:49 UTCVendor advisory
  24. 2026-09-21 15:49 UTCGHSA enrichment
  25. 2026-09-20 20:16 UTCEPSS rescore
Show 68 more
  1. 2026-09-20 17:37 UTCVendor advisory
  2. 2026-09-20 17:36 UTCGHSA enrichment
  3. 2026-09-19 19:16 UTCEG score recompute
  4. 2026-09-19 19:16 UTCVendor advisory
  5. 2026-09-19 19:16 UTCGHSA enrichment
  6. 2026-09-18 20:54 UTCEG score recompute
  7. 2026-09-18 20:54 UTCVendor advisory
  8. 2026-09-18 20:54 UTCGHSA enrichment
  9. 2026-09-18 19:28 UTCEPSS rescore
  10. 2026-09-18 14:05 UTCVendor advisory
  11. 2026-09-18 14:05 UTCGHSA enrichment
  12. 2026-09-17 23:20 UTCVendor advisory
  13. 2026-09-17 23:20 UTCGHSA enrichment
  14. 2026-09-17 20:05 UTCEG score recompute
  15. 2026-09-17 20:05 UTCVendor advisory
  16. 2026-09-17 20:05 UTCGHSA enrichment
  17. 2026-09-16 22:04 UTCEG score recompute
  18. 2026-09-16 22:04 UTCVendor advisory
  19. 2026-09-16 22:04 UTCGHSA enrichment
  20. 2026-09-16 19:37 UTCEG score recompute
  21. 2026-09-16 19:37 UTCVendor advisory
  22. 2026-09-16 19:37 UTCGHSA enrichment
  23. 2026-09-16 14:08 UTCEPSS rescore
  24. 2026-09-16 05:15 UTCEPSS rescore
  25. 2026-09-15 22:49 UTCVendor advisory
  26. 2026-09-15 22:49 UTCGHSA enrichment
  27. 2026-09-15 17:44 UTCEG score recompute
  28. 2026-09-15 17:44 UTCVendor advisory
  29. 2026-09-15 17:44 UTCGHSA enrichment
  30. 2026-09-14 23:00 UTCVendor advisory
  31. 2026-09-14 23:00 UTCGHSA enrichment
  32. 2026-09-14 17:31 UTCVendor advisory
  33. 2026-09-14 17:31 UTCGHSA enrichment
  34. 2026-09-14 17:07 UTCVendor advisory
  35. 2026-09-14 17:07 UTCGHSA enrichment
  36. 2026-09-13 18:54 UTCEG score recompute
  37. 2026-09-13 18:54 UTCVendor advisory
  38. 2026-09-13 18:54 UTCGHSA enrichment
  39. 2026-09-12 20:40 UTCEG score recompute
  40. 2026-09-12 20:40 UTCVendor advisory
  41. 2026-09-12 20:40 UTCGHSA enrichment
  42. 2026-09-11 22:27 UTCVendor advisory
  43. 2026-09-11 22:27 UTCGHSA enrichment
  44. 2026-09-11 19:56 UTCVendor advisory
  45. 2026-09-11 19:56 UTCGHSA enrichment
  46. 2026-09-11 16:54 UTCEG score recompute
  47. 2026-09-11 16:54 UTCVendor advisory
  48. 2026-09-11 16:54 UTCGHSA enrichment
  49. 2026-09-11 14:53 UTCEPSS rescore
  50. 2026-09-11 09:37 UTCEPSS rescore
  51. 2026-09-10 23:21 UTCGHSA enrichment
  52. 2026-09-10 19:54 UTCEG score recompute
  53. 2026-09-10 19:54 UTCGHSA enrichment
  54. 2026-09-09 21:41 UTCVendor advisory
  55. 2026-09-09 21:41 UTCGHSA enrichment
  56. 2026-09-09 19:55 UTCVendor advisory
  57. 2026-09-09 19:55 UTCGHSA enrichment
  58. 2026-09-08 23:52 UTCEG score recompute
  59. 2026-09-08 23:52 UTCVendor advisory
  60. 2026-09-08 23:51 UTCGHSA enrichment
  61. 2026-09-08 21:45 UTCEG score recompute
  62. 2026-09-08 21:45 UTCVendor advisory
  63. 2026-09-08 21:45 UTCGHSA enrichment
  64. 2026-09-08 20:50 UTCEG score recompute
  65. 2026-09-08 19:32 UTCEG score recompute
  66. 2026-09-08 18:50 UTCEG score recompute
  67. 2026-09-08 18:50 UTCVendor advisory
  68. 2026-09-08 18:49 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-66303?
CVE-2026-66303 is a medium vulnerability published on September 8, 2026. Null pointer dereference in Skype for Business allows an authorized attacker to deny service over a network.
When was CVE-2026-66303 disclosed?
CVE-2026-66303 was first published in the National Vulnerability Database on September 8, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66303 actively exploited?
CVE-2026-66303 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 34.9% of all scored CVEs.
What is the CVSS score of CVE-2026-66303?
CVE-2026-66303 has a CVSS v4.0 base score of 6.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-66303?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66303, 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-2026-66303

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