CVE-2021-33771

HIGHNVD 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
7.8
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 6%CVSS: 7.8Exploit: NoneExposed: 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
92.8%
KEV
⚠ Exploited

Published

July 14, 2021

Last Modified

October 29, 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-2021-33771
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

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 77× in last 7d / 387× 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 732 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2021-33771?
CVE-2021-33771 is a high 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 October 29, 2025. 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

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