CVE-2021-34450

CRITICALNVD 9.99.9—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.9 under NVD CVSS v3. EPSS exploit probability: 2.5% (84th percentile of EPSS-scored CVEs). GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
9.9EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 2.5%CVSS: 9.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Windows Hyper-V Remote Code Execution Vulnerability

CVSS v3
9.9
EG Score
9.9CRITICALmedium confidence
EG Risk
50
EG Risk 50/100CISA SSVC

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
Severity99% × 45%
Exploitation3% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track* or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
2.5%
EPSS %ILE
84th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact total (CVSS ≥ 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 16, 2021

Last Modified

August 10, 2026

Advisory Details (2)

Auto-updated Sep 28, 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://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34450
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-2021-34450

Vendor Advisories for CVE-2021-34450(2)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 31× 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. 2026-10-03 14:22 UTCEPSS rescore
  2. 2026-10-01 19:46 UTCEPSS rescore
  3. 2026-09-30 15:37 UTCEG score recompute
  4. 2026-09-30 15:00 UTCEPSS rescore
  5. 2026-09-29 15:15 UTCEPSS rescore
  6. 2026-09-28 13:47 UTCEPSS rescore
  7. 2026-09-27 13:41 UTCEPSS rescore
  8. 2026-09-26 15:54 UTCEPSS rescore
  9. 2026-09-26 00:21 UTCEPSS rescore
  10. 2026-09-24 14:00 UTCEPSS rescore
  11. 2026-09-23 13:44 UTCEPSS rescore
  12. 2026-09-22 14:44 UTCEPSS rescore
  13. 2026-09-21 20:28 UTCEPSS rescore
  14. 2026-09-21 20:28 UTCEPSS rescore
  15. 2026-09-20 20:12 UTCEPSS rescore
  16. 2026-09-19 15:38 UTCEPSS rescore
  17. 2026-09-18 19:23 UTCEPSS rescore
  18. 2026-09-17 19:23 UTCEPSS rescore
  19. 2026-09-17 19:23 UTCEPSS rescore
  20. 2026-09-16 14:05 UTCEPSS rescore
  21. 2026-09-16 14:05 UTCEPSS rescore
  22. 2026-09-15 03:06 UTCEPSS rescore
  23. 2026-09-13 16:43 UTCEPSS rescore
  24. 2026-09-12 14:57 UTCEPSS rescore
  25. 2026-09-11 14:49 UTCEPSS rescore
Show 75 more
  1. 2026-09-11 09:33 UTCEPSS rescore
  2. 2026-09-08 21:56 UTCEPSS rescore
  3. 2026-09-07 15:58 UTCEPSS rescore
  4. 2026-09-06 13:45 UTCEPSS rescore
  5. 2026-09-06 13:45 UTCEPSS rescore
  6. 2026-09-05 15:25 UTCEPSS rescore
  7. 2026-09-04 13:57 UTCEPSS rescore
  8. 2026-09-04 05:03 UTCEPSS rescore
  9. 2026-09-02 14:08 UTCEPSS rescore
  10. 2026-09-01 13:50 UTCEPSS rescore
  11. 2026-09-01 03:32 UTCEPSS rescore
  12. 2026-08-30 19:14 UTCEPSS rescore
  13. 2026-08-30 01:19 UTCEPSS rescore
  14. 2026-08-30 01:19 UTCEPSS rescore
  15. 2026-08-28 21:37 UTCEPSS rescore
  16. 2026-08-27 14:22 UTCEPSS rescore
  17. 2026-08-26 14:42 UTCEPSS rescore
  18. 2026-08-25 13:46 UTCEPSS rescore
  19. 2026-08-24 14:13 UTCEPSS rescore
  20. 2026-08-23 00:16 UTCEPSS rescore
  21. 2026-08-21 23:46 UTCEPSS rescore
  22. 2026-08-20 22:52 UTCEPSS rescore
  23. 2026-08-19 17:01 UTCEPSS rescore
  24. 2026-08-18 13:45 UTCEPSS rescore
  25. 2026-08-17 13:44 UTCEPSS rescore
  26. 2026-08-16 14:53 UTCEPSS rescore
  27. 2026-08-16 02:11 UTCEPSS rescore
  28. 2026-08-16 02:11 UTCEPSS rescore
  29. 2026-08-15 01:27 UTCEPSS rescore
  30. 2026-08-13 21:57 UTCEPSS rescore
  31. 2026-08-12 13:48 UTCEPSS rescore
  32. 2026-08-11 13:38 UTCEPSS rescore
  33. 2026-08-10 16:33 UTCEG score recompute▲ 1.40
  34. 2026-08-10 16:33 UTCGHSA enrichment
  35. 2026-08-10 16:19 UTCNVD updateCVSS v3 → 9.9 · severity → CRITICAL
  36. 2026-08-10 15:50 UTCEG score recompute
  37. 2026-08-10 15:50 UTCGHSA enrichment
  38. 2026-08-09 13:44 UTCEPSS rescore
  39. 2026-08-08 16:33 UTCEPSS rescore
  40. 2026-08-07 16:24 UTCEPSS rescore
  41. 2026-08-06 13:43 UTCEPSS rescore
  42. 2026-08-05 19:14 UTCEPSS rescore
  43. 2026-08-04 15:06 UTCEPSS rescore
  44. 2026-08-04 10:34 UTCEPSS rescore
  45. 2026-08-03 10:33 UTCEPSS rescore
  46. 2026-08-02 02:24 UTCEPSS rescore
  47. 2026-08-02 02:24 UTCEPSS rescore
  48. 2026-08-01 04:13 UTCEPSS rescore
  49. 2026-07-30 16:25 UTCEPSS rescore
  50. 2026-07-30 01:28 UTCEPSS rescore
  51. 2026-07-28 15:33 UTCEPSS rescore
  52. 2026-07-26 14:52 UTCEPSS rescore
  53. 2026-07-26 14:52 UTCEPSS rescore
  54. 2026-07-25 14:15 UTCEPSS rescore
  55. 2026-07-24 14:15 UTCEPSS rescore
  56. 2026-07-23 14:16 UTCEPSS rescore
  57. 2026-07-23 14:16 UTCEPSS rescore
  58. 2026-07-23 02:01 UTCEG score recompute
  59. 2026-07-22 22:48 UTCEG score recompute
  60. 2026-07-22 14:06 UTCEPSS rescore
  61. 2026-07-22 14:06 UTCEPSS rescore
  62. 2026-07-21 15:22 UTCEPSS rescore
  63. 2026-07-21 15:22 UTCEPSS rescore
  64. 2026-07-20 17:05 UTCEPSS rescore
  65. 2026-07-19 14:29 UTCEPSS rescore
  66. 2026-07-19 14:29 UTCEPSS rescore
  67. 2026-07-19 02:27 UTCEPSS rescore
  68. 2026-07-18 10:02 UTCEPSS rescore
  69. 2026-07-18 10:02 UTCEPSS rescore
  70. 2026-07-16 17:00 UTCEPSS rescore
  71. 2026-07-16 17:00 UTCEPSS rescore
  72. 2026-07-15 16:55 UTCEPSS rescore
  73. 2026-07-15 01:58 UTCEPSS rescore
  74. 2026-07-13 22:27 UTCEPSS rescore
  75. 2026-07-13 06:10 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-34450?
CVE-2021-34450 is a critical vulnerability published on July 16, 2021. Windows Hyper-V Remote Code Execution Vulnerability
When was CVE-2021-34450 disclosed?
CVE-2021-34450 was first published on July 16, 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-2021-34450 actively exploited?
CVE-2021-34450 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.5% probability of exploitation in the next 30 days (84th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-34450?
CVE-2021-34450 has a CVSS v3 base score of 9.9 (NVD).
How do I remediate CVE-2021-34450?
A fix for CVE-2021-34450 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-34450 are linked in the Vendor Advisories panel on this page.

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