CVE-2025-21335: Microsoft Windows Hyper-V NT Kernel Integration VSP Use-After-Free Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 14 Jan 2025, the same day the CVE record was published.

How likely is exploitation in the next 30 days?

1.4%

EPSS score, percentile 72.4 of all scored records

How severe?

7.8 High

CVSS v3.1 base score, given by the CNA

What should I do?

CISA deadline 4 Feb 2025. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Advisories and patches (1)

Which versions are affected?

Affected

• from 10.0.19044.0 to before 10.0.19044.5371
• from 10.0.19045.0 to before 10.0.19045.5371
• from 10.0.22621.0 to before 10.0.22621.4751
• from 10.0.22631.0 to before 10.0.22631.4751
• from 10.0.22631.0 to before 10.0.22631.4751
• from 10.0.26100.0 to before 10.0.26100.2894

and 3 more in the table below

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 4 February 2025.

Advisories and patches

• Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability (Vendor advisory, Patch)

Linked from CISA's catalog entry

• https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-21335
• https://nvd.nist.gov/vuln/detail/CVE-2025-21335

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

Microsoft Windows Hyper-V NT Kernel Integration VSP contains a use-after-free vulnerability that allows a local attacker to gain SYSTEM privileges.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2025-21335 to its Known Exploited Vulnerabilities (KEV) catalog on 14 Jan 2025.
• CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
• The due date CISA sets for the required action is 4 Feb 2025.
• The CVE record was published on 14 Jan 2025, the same day it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 7.8 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 1.4% (percentile 72.4), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

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

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

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-416: Use After Free

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

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