CVE-2026-55040

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreHIGH confidence

Score elevated to 9.1 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2026-08-18), indicating real-world exploitation has been confirmed by US federal agencies. the CNA's CVSS baseline 9.1 retained for reference (NVD's own analysis pending). Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, cna:microsoft, epss, ghsa
Trending — 5 sources updated this weekExploited in the wild
9.1EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 51%CVSS: 9.1Exploit: cisa kev · ssvc active · epss top5pct · epss high · public exploitExposed: 0

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

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

CVSS v3
9.1
EG Score
9.1(high)
EG Risk
96(Act)
EG Risk 96/100SSVC: Act

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
Severity91% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
51%
EPSS %ILE
99%
KEV
⚠ Exploited

Published

July 14, 2026

Last Modified

September 17, 2026

Advisory Details (1)

Auto-updated Sep 15, 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-2026-55040

Vendor Advisories for CVE-2026-55040(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 95× in last 7d / 399× 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 802 total refreshes for this CVE.

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

Publicly available exploits

(3 references)

Working exploit code is in the public domain (2 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCsfewer-r7/CVE-2026-55040
    First seen Aug 6, 2026

    Microsoft SharePoint JWT Authentication Bypass (CVE-2026-55040)

    Open source ↗
  • GitHub PoCl0ggg/CVE-2026-55040
    First seen Jul 28, 2026

    Exploit code for CVE-2026-55040, it can create auth header for any validate account.

    Open source ↗
  • Nucleijavascript/cves/2026/CVE-2026-55040.yaml
    First seen Jan 1, 2026

    Microsoft SharePoint Server - JWT Authentication Bypass

    Open source ↗

Frequently asked(6)

What is CVE-2026-55040?
CVE-2026-55040 is a critical vulnerability published on July 14, 2026. Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
When was CVE-2026-55040 disclosed?
CVE-2026-55040 was first published in the National Vulnerability Database on July 14, 2026, with the most recent update on September 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55040 actively exploited?
Yes. CISA added CVE-2026-55040 to the Known Exploited Vulnerabilities catalog on August 18, 2026, affecting Microsoft SharePoint. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2026-55040?
CVE-2026-55040 has a CVSS v4.0 base score of 9.1 (CNA self-assessment; NVD's own analysis pending).
Which products are affected by CVE-2026-55040?
CVE-2026-55040 affects Microsoft SharePoint. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2026-55040?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55040, 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-2026-55040

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