PatchSiren

PatchSiren cyber security CVE debrief

CVE-2025-21333 Microsoft CVE debrief

CVE-2025-21333 is a Microsoft Windows Hyper-V NT Kernel Integration VSP heap-based buffer overflow. CISA added it to the Known Exploited Vulnerabilities catalog on 2025-01-14, so defenders should treat it as a high-priority issue for Windows systems that use the affected virtualization component. The supplied corpus does not include full vendor advisory text or a CVSS score, so remediation guidance here is limited to the official KEV-driven action: apply vendor mitigations or discontinue use if mitigations are unavailable.

Vendor
Microsoft
Product
Windows
CVSS
HIGH 7.8
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 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.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-21333 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-21333

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2025-21333 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-21333

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.