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CVE-2025-21334 Microsoft CVE debrief

CVE-2025-21334 is a Microsoft Windows Hyper-V NT Kernel Integration VSP use-after-free vulnerability. CISA added it to the Known Exploited Vulnerabilities catalog on 2025-01-14, which means defenders should treat it as a high-priority issue even though no CVSS score was provided in the supplied record. The safest response is to follow Microsoft’s guidance, apply any available remediation as soon as possible, and use CISA’s required-action guidance if mitigation is not immediately available.

Vendor
Microsoft
Product
Windows
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2025-01-14
Original CVE updated
2025-01-14
Advisory published
2025-01-14
Advisory updated
2025-01-14

Who should care

Windows administrators, virtualization and infrastructure teams, and security operations staff responsible for Microsoft Hyper-V environments should prioritize this CVE. It is especially relevant for systems that run or depend on the Hyper-V NT Kernel Integration VSP component and for organizations that track CISA KEV items as part of patch SLAs.

Technical summary

The supplied record describes a use-after-free condition in Microsoft Windows Hyper-V NT Kernel Integration VSP. A use-after-free is a memory-safety flaw that can lead to unstable or unsafe behavior in the affected component. The record does not include exploit mechanics, impact details, or a CVSS score, so the defensible summary is limited to the vulnerability class, affected Microsoft Windows/Hyper-V component, and the fact that CISA has placed it in KEV.

Defensive priority

Immediate. CISA listed this CVE in KEV on 2025-01-14 with a due date of 2025-02-04, so organizations should accelerate remediation and confirm exposure quickly.

Recommended defensive actions

  • Review Microsoft’s advisory for CVE-2025-21334 and apply the vendor-recommended update or mitigation as soon as possible.
  • Check whether any Windows systems in your environment use Hyper-V or related virtualization features that rely on the NT Kernel Integration VSP component.
  • Prioritize this CVE in patch workflows because it is listed in CISA’s Known Exploited Vulnerabilities catalog.
  • If a mitigation is not available, follow CISA’s guidance to discontinue use of the affected product or feature until remediation is possible.
  • Verify remediation by rechecking asset inventory, patch state, and any compensating controls after updates are deployed.

Evidence notes

This debrief is based only on the supplied CVE metadata and official resource links. The record names the issue as a Microsoft Windows Hyper-V NT Kernel Integration VSP use-after-free vulnerability, shows published and modified dates of 2025-01-14, and includes CISA KEV metadata with dateAdded 2025-01-14 and dueDate 2025-02-04. No CVSS score, exploit details, or vendor advisory contents were provided in the corpus.

Official resources

Published from the supplied CVE and CISA KEV metadata only. No exploit code, reproduction steps, or vendor advisory details were used beyond the official links provided in the corpus.