CVE-2025-21333 Microsoft CVE debrief

Who should care

Windows administrators, virtualization and platform teams, and security operations staff responsible for Microsoft Hyper-V hosts or other Windows systems that rely on the NT Kernel Integration VSP component.

Technical summary

The vulnerability is described as a heap-based buffer overflow in Microsoft Windows Hyper-V NT Kernel Integration VSP. The supplied sources do not provide deeper impact details, exploit mechanics, or a CVSS score, but CISA's KEV listing confirms it is considered known exploited.

Defensive priority

Urgent. A CISA KEV listing means this issue should be prioritized ahead of non-KEV vulnerabilities, with particular focus on exposed or production Windows Hyper-V environments.

Recommended defensive actions

• Review Microsoft and CISA references for the affected Windows versions and any vendor-provided mitigation or patch guidance.
• Apply Microsoft updates or mitigations as soon as they are available for affected Windows and Hyper-V systems.
• If mitigations are unavailable for a system that must remain online, follow CISA guidance to discontinue use of the product or component where feasible.
• Prioritize remediation before the CISA KEV due date of 2025-02-04.
• Inventory Windows hosts that use Hyper-V and NT Kernel Integration VSP so remediation can be verified quickly.

Evidence notes

The CISA Known Exploited Vulnerabilities entry names CVE-2025-21333 as Microsoft Windows Hyper-V NT Kernel Integration VSP Heap-based Buffer Overflow Vulnerability and lists dateAdded 2025-01-14 with dueDate 2025-02-04. The supplied corpus also includes the CVE record and NVD detail links, but no CVSS score or extended vendor advisory text.

Official resources