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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 4 Feb 2025.
Windows 10 21h2Operating system · Microsoft

CVE-2025-21333

HIGH · 7.8 CVSS v3.1 Published 2025-01-14
Fix available
A fix is available. Upgrade to 10.0.19044.5371 / 10.0.19045.5371 or later.
See remediation →
96/100
Remediation priority · Urgent
In the wild Public exploit Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is an elevation of privilege vulnerability in the NT Kernel Integration VSP (Virtual Service Provider) component of Windows Hyper-V. The vulnerability would allow an authenticated attacker to elevate their privileges within the Hyper-V virtualization environment, potentially escaping VM isolation to compromise the host system.

MitigationApply the Microsoft security update for CVE-2025-21333 to all affected Windows Hyper-V hosts. Prioritize patching systems with direct network exposure and those hosting untrusted workloads.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 21h2Operating system
Affected:< 10.0.19044.5371
Windows 10 22h2Operating system
Affected:< 10.0.19045.5371
Windows 11 22h2Operating system
Affected:< 10.0.22621.4751
Windows 11 23h2Operating system
Affected:< 10.0.22631.4751
Windows 11 24h2Operating system
Affected:< 10.0.26100.2894
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.1369
Windows Server 2025Operating system
Affected:< 10.0.26100.2894

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Hyper-V is enabled on the system
    Run 'Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V' in PowerShell, or check in Windows Features that Hyper-V is installed. On Server, run 'Get-WindowsFeature -Name Hyper-V'.
    Affected if Hyper-V role or feature is installed and enabled - the vulnerability only affects systems with Hyper-V present
  2. Determine the installed Windows build number
    Run 'winver' from the Run dialog, or run 'systeminfo' in Command Prompt, or use 'Get-ComputerInfo | Select-Object WindowsVersion,OsBuildNumber' in PowerShell.
    Affected if The build number shown is below the fixed version for your specific Windows release (see affected version ranges)
  3. Compare your Windows version to affected ranges
    Match your Windows edition (Windows 10 21h2, 22h2, Windows 11 22h2, 23h2, 24h2, Server 2022 23h2, or Server 2025) and compare the build number to: 19044.5371, 19045.5371, 22621.4751, 22631.4751, 26100.2894, 25398.1369 respectively.
    Affected if Your build number is less than the corresponding threshold for your Windows version - this indicates the vulnerability is present

You are affected if Hyper-V is installed on the system AND the Windows build number is below the fixed version for your specific Windows release.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.19044.5371 / 10.0.19045.5371 / 10.0.22621.4751 or later
Fixed in 10.0.19044.537110.0.19045.537110.0.22621.4751
Vendor patch msrc.microsoft.com →
Interim mitigation

Apply the Microsoft security update for CVE-2025-21333 to all affected Windows Hyper-V hosts. Prioritize patching systems with direct network exposure and those hosting untrusted workloads.

Recommended fix High confidence

Windows 10 21h2: build 10.0.19044.5371 | Windows 10 22h2: build 10.0.19045.5371 | Windows 11 22h2: build 10.0.22621.4751 | Windows 11 23h2: build 10.0.22631.4751 | Windows 11 24h2: build 10.0.26100.2894 | Windows Server 2022 23h2: build 10.0.25398.1369 | Windows Server 2025: build 10.0.26100.2894

  1. Open Settings > Update & Security > Windows Update and check for updates
  2. If updates are available, install all pending Windows security updates
  3. Alternatively, manually download and install the specificKB update for your Windows version from the Microsoft Update Catalog
  4. Restart the system after installing updates
  5. Verify the installation by running 'winver' to confirm the build number matches or exceeds the fixed version for your release
Caveat Standard Windows updateapply risk; ensure backups and test in non-production environments before deploying enterprise-wide

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 10 21h2 Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-21333 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21333 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data