CVE-2021-33771

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 2021-11-03), 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: 10%CVSS: 7.8Exploit: cisa kev · ssvc active · epss top5pctExposed: 0

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

Windows Kernel 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
10%
EPSS %ILE
95%
KEV
⚠ Exploited

Published

July 14, 2021

Last Modified

August 10, 2026

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-2021-33771
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-2021-33771

Vendor Advisories for CVE-2021-33771(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(2)

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 102× in last 7d / 419× 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 1,512 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2021-33771?
CVE-2021-33771 is a critical vulnerability published on July 14, 2021. Windows Kernel Elevation of Privilege Vulnerability
When was CVE-2021-33771 disclosed?
CVE-2021-33771 was first published in the National Vulnerability Database on July 14, 2021, with the most recent update on August 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-33771 actively exploited?
Yes. CISA added CVE-2021-33771 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Microsoft Windows. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-33771?
CVE-2021-33771 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-2021-33771?
CVE-2021-33771 affects Microsoft Windows. 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-2021-33771?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33771, 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-2021-33771

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