VulnerabilityAnalyzed

CVE-2026-21247

Improper input validation in Windows Hyper-V allows an authorized attacker to execute code locally.

HIGH 7.3EPSS 0.57%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.57%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

Improper input validation in Windows Hyper-V allows an authorized attacker to execute code locally.

CVSS 3.1: 7.3 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
EPSS: 0.57% probability · 45th percentile
CISA KEV: Not listed
Weakness: CWE-20, CWE-122, CWE-125
Affected: microsoft/windows 10 1607 · microsoft/windows 10 1809 · microsoft/windows 10 21h2 · microsoft/windows 10 22h2 · microsoft/windows 11 23h2 · microsoft/windows 11 24h2 · microsoft/windows 11 25h2 · microsoft/windows server 2016 · microsoft/windows server 2019 · microsoft/windows server 2022 · microsoft/windows server 2022 23h2 · microsoft/windows server 2025
Source: secure@microsoft.com

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21247Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.