CVE-2026-40403

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-05-12. the CNA's CVSS baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.8Exploit: NoneExposed: 0

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

Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.

CVSS v3
8.8
EG Score
8.8(medium)
EPSS
34.5%
KEV
Not listed

Published

May 12, 2026

Last Modified

June 19, 2026

Advisory Details (1)

Auto-updated May 12, 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-2026-40403

Vendor Advisories for CVE-2026-40403(1)

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 8× in last 7d / 61× 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 180 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-40403?
CVE-2026-40403 is a high vulnerability published on May 12, 2026. Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.
When was CVE-2026-40403 disclosed?
CVE-2026-40403 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on June 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-40403 actively exploited?
CVE-2026-40403 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 34.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-40403?
CVE-2026-40403 has a CVSS v4.0 base score of 8.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-40403?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40403, 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-2026-40403

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