Security Digest · Vulnerability record · Known exploited
CVE-2025-21333: Microsoft Windows Hyper-V NT Kernel Integration VSP Heap-based Buffer Overflow Vulnerability
Exploited in the wild (CISA KEV). Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability
CISA KEV · added 2025-01-14 CVSS 7.8 High EPSS 10.1% · p96
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-01-14, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-02-04; treat that as the outer limit, not the target.
- EPSS 10.1%, percentile 96: FIRST’s model estimates a 10.1% chance of exploitation activity in the next 30 days, higher than 96% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
What it is
Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability
CISA’s summary
Microsoft Windows Hyper-V NT Kernel Integration VSP contains a heap-based buffer overflow vulnerability that allows a local attacker to gain SYSTEM privileges.
Weakness type: CWE-122.
Product: Microsoft Windows · Assigned by: microsoft · Published: 2025-01-14
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 < 10.0.19044.5371 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 < 10.0.19045.5371 |
| Microsoft | Windows 11 version 22H2 | 10.0.22621.0 < 10.0.22621.4751 |
| Microsoft | Windows 11 version 22H3 | 10.0.22631.0 < 10.0.22631.4751 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 < 10.0.22631.4751 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 < 10.0.26100.2894 |
| Microsoft | Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.0 < 10.0.25398.1369 |
| Microsoft | Windows Server 2025 | 10.0.26100.0 < 10.0.26100.2894 |
| Microsoft | Windows Server 2025 (Server Core installation) | 10.0.26100.0 < 10.0.26100.2894 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 7.8 High | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C |
- Attack vector: local access needed
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2025-01-14; federal due date 2025-02-04. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 10.07% probability of exploitation activity in the next 30 days; percentile 96.
Timeline
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by microsoft
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability msrc.microsoft.com
- Listed in CISA KEV notes (msrc.microsoft.com) msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2025-21333 cve.org
- NVD entry CVE-2025-21333 nvd.nist.gov
Government
Other references from the CVE record and advisory
- vicarius.io vicarius.io
- vicarius.io vicarius.io
- exploit-db.com exploit-db.com
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