CVE-2026-54998

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-07-03. the CNA's CVSS baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
Trending — 4 sources updated this weekElevated
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.8Exploit: Elevated riskExposed: 0

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

Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.

CVSS v3
8.8
EG Score
8.8(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: 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
Severity88% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
54%
KEV
Not listed

Published

July 2, 2026

Last Modified

September 9, 2026

Advisory Details (1)

Auto-updated Jul 3, 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-2026-54998

Vendor Advisories for CVE-2026-54998(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 18× in last 7d / 120× 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 318 total refreshes for this CVE.

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

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCsentinel-aidefense/CVE-2026-54998-exp
    First seen Jul 4, 2026

    CVE-2026-54998 RCE Exploit

    Open source ↗

Frequently asked(5)

What is CVE-2026-54998?
CVE-2026-54998 is a high vulnerability published on July 2, 2026. Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.
When was CVE-2026-54998 disclosed?
CVE-2026-54998 was first published in the National Vulnerability Database on July 2, 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-2026-54998 actively exploited?
CVE-2026-54998 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 46.2% of all scored CVEs.
What is the CVSS score of CVE-2026-54998?
CVE-2026-54998 has a CVSS v4.0 base score of 8.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-54998?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54998, 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-2026-54998

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