CVE-2026-56191

CRITICALPre-NVD 10.010.0—
EchelonGraph scoreMEDIUM confidence

Score 10.0 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-24. the CNA's CVSS baseline 10.0; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
Trending — 4 sources updated this week
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 10.0Exploit: None knownExposed: 0

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

Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.

CVSS v3
10.0
EG Score
10.0(medium)
EG Risk
60(Track)
EG Risk 60/100SSVC: 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
Severity100% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
53%
KEV
Not listed

Published

July 24, 2026

Last Modified

September 9, 2026

Advisory Details (1)

Auto-updated Sep 9, 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-2026-56191

Vendor Advisories for CVE-2026-56191(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 56× in last 7d / 286× 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 608 total refreshes for this CVE.

  1. 2026-09-15 09:45 UTCEG score recompute
  2. 2026-09-15 09:45 UTCVendor advisory
  3. 2026-09-15 09:45 UTCGHSA enrichment
  4. 2026-09-15 03:11 UTCEPSS rescore
  5. 2026-09-14 16:10 UTCVendor advisory
  6. 2026-09-14 16:10 UTCGHSA enrichment
  7. 2026-09-14 09:24 UTCVendor advisory
  8. 2026-09-14 09:24 UTCGHSA enrichment
  9. 2026-09-14 05:43 UTCVendor advisory
  10. 2026-09-14 05:43 UTCGHSA enrichment
  11. 2026-09-14 02:02 UTCVendor advisory
  12. 2026-09-14 02:02 UTCGHSA enrichment
  13. 2026-09-13 22:21 UTCEG score recompute
  14. 2026-09-13 22:21 UTCVendor advisory
  15. 2026-09-13 22:21 UTCGHSA enrichment
  16. 2026-09-13 16:47 UTCEPSS rescore
  17. 2026-09-13 15:28 UTCVendor advisory
  18. 2026-09-13 15:28 UTCGHSA enrichment
  19. 2026-09-13 11:15 UTCVendor advisory
  20. 2026-09-13 11:15 UTCGHSA enrichment
  21. 2026-09-13 07:34 UTCVendor advisory
  22. 2026-09-13 07:34 UTCGHSA enrichment
  23. 2026-09-13 03:52 UTCVendor advisory
  24. 2026-09-13 03:52 UTCGHSA enrichment
  25. 2026-09-13 00:11 UTCVendor advisory
Show 75 more
  1. 2026-09-13 00:11 UTCGHSA enrichment
  2. 2026-09-12 20:23 UTCVendor advisory
  3. 2026-09-12 20:23 UTCGHSA enrichment
  4. 2026-09-12 16:36 UTCEG score recompute
  5. 2026-09-12 16:36 UTCVendor advisory
  6. 2026-09-12 16:36 UTCGHSA enrichment
  7. 2026-09-12 12:55 UTCVendor advisory
  8. 2026-09-12 12:55 UTCGHSA enrichment
  9. 2026-09-12 09:14 UTCVendor advisory
  10. 2026-09-12 09:14 UTCGHSA enrichment
  11. 2026-09-12 05:06 UTCVendor advisory
  12. 2026-09-12 05:06 UTCGHSA enrichment
  13. 2026-09-12 00:49 UTCVendor advisory
  14. 2026-09-12 00:49 UTCGHSA enrichment
  15. 2026-09-11 20:27 UTCVendor advisory
  16. 2026-09-11 20:27 UTCGHSA enrichment
  17. 2026-09-11 16:40 UTCEG score recompute
  18. 2026-09-11 16:40 UTCVendor advisory
  19. 2026-09-11 16:40 UTCGHSA enrichment
  20. 2026-09-11 14:53 UTCEPSS rescore
  21. 2026-09-11 07:11 UTCGHSA enrichment
  22. 2026-09-11 03:02 UTCGHSA enrichment
  23. 2026-09-10 20:55 UTCGHSA enrichment
  24. 2026-09-10 15:03 UTCEG score recompute
  25. 2026-09-10 15:03 UTCGHSA enrichment
  26. 2026-09-10 09:35 UTCEPSS rescore
  27. 2026-09-09 21:06 UTCVendor advisory
  28. 2026-09-09 21:06 UTCGHSA enrichment
  29. 2026-09-09 08:53 UTCEG score recompute
  30. 2026-09-09 08:53 UTCVendor advisory
  31. 2026-09-09 08:53 UTCGHSA enrichment
  32. 2026-09-08 22:01 UTCEPSS rescore
  33. 2026-09-08 21:05 UTCGHSA enrichment
  34. 2026-09-08 17:14 UTCVendor advisory
  35. 2026-09-08 17:14 UTCGHSA enrichment
  36. 2026-09-08 01:09 UTCVendor advisory
  37. 2026-09-08 01:09 UTCGHSA enrichment
  38. 2026-09-07 21:28 UTCEG score recompute
  39. 2026-09-07 21:28 UTCVendor advisory
  40. 2026-09-07 21:27 UTCGHSA enrichment
  41. 2026-09-07 16:01 UTCEPSS rescore
  42. 2026-09-06 16:39 UTCEG score recompute
  43. 2026-09-06 16:39 UTCVendor advisory
  44. 2026-09-06 16:39 UTCGHSA enrichment
  45. 2026-09-06 13:47 UTCEPSS rescore
  46. 2026-09-06 12:32 UTCVendor advisory
  47. 2026-09-06 12:32 UTCGHSA enrichment
  48. 2026-09-06 08:25 UTCVendor advisory
  49. 2026-09-06 08:24 UTCGHSA enrichment
  50. 2026-09-06 02:50 UTCVendor advisory
  51. 2026-09-06 02:50 UTCGHSA enrichment
  52. 2026-09-05 23:09 UTCVendor advisory
  53. 2026-09-05 23:09 UTCGHSA enrichment
  54. 2026-09-05 19:27 UTCEG score recompute
  55. 2026-09-05 19:27 UTCVendor advisory
  56. 2026-09-05 19:27 UTCGHSA enrichment
  57. 2026-09-05 06:56 UTCVendor advisory
  58. 2026-09-05 06:56 UTCGHSA enrichment
  59. 2026-09-04 22:35 UTCVendor advisory
  60. 2026-09-04 22:35 UTCGHSA enrichment
  61. 2026-09-04 17:05 UTCEG score recompute
  62. 2026-09-04 17:05 UTCVendor advisory
  63. 2026-09-04 17:05 UTCGHSA enrichment
  64. 2026-09-04 12:57 UTCEG score recompute
  65. 2026-09-04 12:57 UTCVendor advisory
  66. 2026-09-04 12:57 UTCGHSA enrichment
  67. 2026-09-04 05:07 UTCEPSS rescore
  68. 2026-09-02 18:41 UTCEG score recompute
  69. 2026-09-02 18:41 UTCGHSA enrichment
  70. 2026-09-02 14:12 UTCEPSS rescore
  71. 2026-09-01 23:20 UTCEG score recompute
  72. 2026-09-01 23:20 UTCVendor advisory
  73. 2026-09-01 23:20 UTCGHSA enrichment
  74. 2026-09-01 13:54 UTCEPSS rescore
  75. 2026-09-01 04:40 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-56191?
CVE-2026-56191 is a critical vulnerability published on July 24, 2026. Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
When was CVE-2026-56191 disclosed?
CVE-2026-56191 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56191 actively exploited?
CVE-2026-56191 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 46.9% of all scored CVEs.
What is the CVSS score of CVE-2026-56191?
CVE-2026-56191 has a CVSS v4.0 base score of 10.0 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-56191?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56191, 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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