High severity · published Feb 10, 2026
CVE-2026-21255
Improper access control in Windows Hyper-V allows an authorized attacker to bypass a security feature locally
8.8
CVSS
0.4%
EPSS
No
On KEV
Description
Improper access control in Windows Hyper-V allows an authorized attacker to bypass a security feature locally.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
W1
Windows 10 1607 · Microsoft
before 10.0.14393.8868 · source: NVD
W1
Windows 10 1809 · Microsoft
before 10.0.17763.8389 · source: NVD
W1
Windows 10 21h2 · Microsoft
before 10.0.19044.6937 · source: NVD
W1
Windows 10 22h2 · Microsoft
before 10.0.19045.6937 · source: NVD
W1
Windows 11 23h2 · Microsoft
before 10.0.22631.6649; before 10.0.22631.6649 · source: NVD
W1
Windows 11 24h2 · Microsoft
before 10.0.26100.7781; before 10.0.26100.7781 · source: NVD
W1
Windows 11 25h2 · Microsoft
before 10.0.26200.7781; before 10.0.26200.7781 · source: NVD
WS
Windows Server 2016 · Microsoft
before 10.0.14393.8868 · source: NVD
WS
Windows Server 2019 · Microsoft
before 10.0.17763.8389 · source: NVD
WS
Windows Server 2022 · Microsoft
before 10.0.20348.4711 · source: NVD
WS
Windows Server 2022 23h2 · Microsoft
before 10.0.25398.2149 · source: NVD
WS
Windows Server 2025 · Microsoft
before 10.0.26100.32313 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21255
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-21255
Vendor Advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21255
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