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CVE-2025-21333

High CVSS 7.8 Known exploited

Published 2025-01-14 · last changed 2026-06-17 · added to CISA KEV 2025-01-14

This one is being exploited in the wild.

CISA added CVE-2025-21333 to the Known Exploited Vulnerabilities catalog on 2025-01-14. Federal agencies are required to remediate it on a deadline. If you have affected machines, this is the class of finding that moves ahead of the rest of the queue.

The fix

Microsoft fixes this in updatesKB5049981, KB5050021, KB5050009, KB5049984. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.

Windows version Fixed in build Update Released
Windows 10 Version 21H2 for x64-based Systems 10.0.19044.5371 KB5049981 2026-09-17
Windows 10 Version 22H2 for x64-based Systems 10.0.19045.5371 KB5049981 2026-09-17
Windows 11 Version 22H2 for ARM64-based Systems 10.0.22621.4751 KB5050021 2026-09-17
Windows 11 Version 22H2 for x64-based Systems 10.0.22621.4751 KB5050021 2026-09-17
Windows 11 Version 23H2 for ARM64-based Systems 10.0.22631.4751 KB5050021 2026-09-17
Windows 11 Version 23H2 for x64-based Systems 10.0.22631.4751 KB5050021 2026-09-17
Windows 11 Version 24H2 for ARM64-based Systems 10.0.26100.2894 KB5050009 2026-09-17
Windows 11 Version 24H2 for x64-based Systems 10.0.26100.2894 KB5050009 2026-09-17
Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1369 KB5049984 2026-09-17
Windows Server 2025 10.0.26100.2894 KB5050009 2026-09-17
Windows Server 2025 (Server Core installation) 10.0.26100.2894 KB5050009 2026-09-17

Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.

What it is

Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability

Sources

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H