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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-2025-21334

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 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 Windows Hyper-V's NT Kernel Integration VSP (Virtual Service Provider). The flaw allows an authenticated attacker to gain elevated privileges within the guest VM, potentially escaping containment boundaries. The vulnerability exists in the kernel-level integration components that handle communication between the host and virtual machines.

MitigationApply the Microsoft security update for CVE-2025-21334 to affected Windows systems running Hyper-V. Test Hyper-V integration services functionality post-patch to ensure VM operations remain stable.

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 installed on the system
    Run 'Get-WindowsOptionalFeature -Online | Where-Object {$_.FeatureName -like "*Hyper-V*"}' in PowerShell or check for Hyper-V in Windows Features. Alternatively, run 'systeminfo' and look for 'Hyper-V' in the OS Configuration section.
    Affected if Hyper-V is enabled or any Hyper-V sub-features are installed, as the vulnerability exists in Hyper-V integration components.
  2. Check the installed Windows version
    Run 'winver', 'systeminfo', or check the registry key 'HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion' to obtain the full version number (for example, 10.0.19044.XXXX).
    Affected if The Windows version is below the fixed version for your specific Windows edition as listed in the affected versions (for Windows 10 21h2: below 10.0.19044.5371; for Windows 10 22h2: below 10.0.19045.5371; for Windows 11 22h2: below 10.0.22621.4751; for Windows 11 23h2: below 10.0.22631.4751; for Win
  3. Confirm the NT Kernel Integration VSP component version
    Check the file version of '%SystemRoot%\System32\drivers\vmswitch.sys' or examine the Hyper-V integration services version via 'Get-Vm' and 'Get-VmIntegrationService' cmdlets in PowerShell if Hyper-V is running.
    Affected if The Hyper-V integration components are present and the Windows version is below the patched build numbers.

You are affected if Hyper-V is enabled on your Windows system AND your installed Windows build number falls below the specific fixed version for your Windows edition as listed in the affected versions.

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-2025-21334 to affected Windows systems running Hyper-V. Test Hyper-V integration services functionality post-patch to ensure VM operations remain stable.

Recommended fix High confidence

Install the February 2025 Windows Security Update (KB5002537 or subsequent cumulative update) matching your OS version - builds 19044.5371, 19045.5371, 22621.4751, 22631.4751, 25398.1369, or 26100.2894 depending on edition

  1. Open Settings > Update & Security > Windows Update and check for updates
  2. Install all cumulative updates and any pending Hyper-V related updates
  3. Verify the installed build number matches or exceeds the fixed version for your Windows release (19044.5371 for 21h2, 19045.5371 for 22h2, 22621.4751 for Win11 22h2, 22631.4751 for Win11 23h2, 26100.2894 for Win11 24h2/Server 2025, 25398.1369 for Server 2022)
  4. Restart the system after updates are installed
  5. For servers, you may also use Windows Server Update Services (WSUS) or Microsoft Update Catalog to deploy the updates
Caveat Standard Windows update risks apply - test in staging environment before broad deployment; ensure backups exist; some updates may require restart

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

Fix this in Windows 10 21h2 Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,040
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,864.

Scan for this in your stack

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dbcve dependency scanner

Check whether your project pulls in CVE-2025-21334 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

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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-2025-21334 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