Your RSA-2048 keys break in 2030. Find every one of them before attackers do.
🛡️
CISA KEV · ACTIVELY EXPLOITED
HIGH severity

CVE-2025-21334 — Windows 10 21h2

HIGH

CVE-2025-21334 is a high-severity (CVSS 7.8) Use After Free vulnerability in microsoft windows 10 21h2. It is in CISA's Known Exploited Vulnerabilities catalog (added 2025-01-14) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.

Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability

Published
Updated
Affected
7 products
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2025-01-14. Federal agencies were required to remediate by 2025-02-04.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2025-21334.

EPSS Exploitation Probability

via FIRST.org ↗
1.6%probability of exploitation in next 30 days
Lower Risk-4.23%
Lower risk than most CVEs75th percentile — riskier than 75% of all scored CVEsHighest risk
0.05%2.75%5.45%8.15%6.6%5.8%1.6%May 26Jun 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2025-21334 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability

Affected Products

7 products · 10 configurations
OS
windows 10 21h2microsoft
< 10.0.19044.5371
range
OS
windows 10 22h2microsoft
< 10.0.19045.5371
range
OS
windows 11 22h2microsoft
< 10.0.22621.4751
range
OS
windows 11 23h2microsoft
< 10.0.22631.4751
range
OS
windows 11 24h2microsoft
< 10.0.26100.2894
range
OS
windows server 2022 23h2microsoft
< 10.0.25398.1369
range

Detection & mitigation playbook

Vendor / appliance

  1. Detect

    Inventory every microsoft windows 10 21h2 deployment and check each version against the affected-products list above.

  2. Fix

    Apply the microsoft windows 10 21h2 security patch or hotfix for CVE-2025-21334 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability
O3 Security · Runtime Protection

Is CVE-2025-21334 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works
CVE-2025-21334: Windows 10 21h2 Use After Free (KEV)