CVE-2021-40450

CRITICALNVD 7.89.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2022-04-25), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 7.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 5 sources updated this weekExploited in the wild
9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 2%CVSS: 7.8Exploit: cisa kev · ssvc activeExposed: 0

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

Win32k Elevation of Privilege Vulnerability

CVSS v3
7.8
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: Attend

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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
2%
EPSS %ILE
80%
KEV
⚠ Exploited

Published

October 13, 2021

Last Modified

October 30, 2025

Advisory Details (2)

Auto-updated Jun 3, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: microsoft, cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40450
microsoft Patch Available

Security Update Guide - Microsoft Security Response Center

Security Update Guide - Microsoft Security Response Center. Patch available via Microsoft Security Update

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40450

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 104× in last 7d / 438× 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 1,432 total refreshes for this CVE.

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

Frequently asked(6)

What is CVE-2021-40450?
CVE-2021-40450 is a critical vulnerability published on October 13, 2021. Win32k Elevation of Privilege Vulnerability
When was CVE-2021-40450 disclosed?
CVE-2021-40450 was first published in the National Vulnerability Database on October 13, 2021, with the most recent update on October 30, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-40450 actively exploited?
Yes. CISA added CVE-2021-40450 to the Known Exploited Vulnerabilities catalog on April 25, 2022, affecting Microsoft Win32k. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-40450?
CVE-2021-40450 has a CVSS v3 base score of 7.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-40450?
CVE-2021-40450 affects Microsoft Win32k. 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-2021-40450?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-40450, 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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