Insufficient granularity of access control in Microsoft Windows and Windows Server - CVE-2026-56155
Published: July 14, 2026
Vulnerability identifier: #VU137539
CSH Severity: High
CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-56155
CWE-ID: CWE-1220
Exploitation vector: Local access
Exploit availability:
The vulnerability is being exploited in the wild
Vulnerability details
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to improper access control in Active Directory Federation Services (AD FS). A local user can escalate privileges on the system.
Note, the vulnerability is being actively exploited in the wild.
Affected software
Microsoft Windows
Windows Server
Windows Server
How to mitigate CVE-2026-56155
Install updates from vendor's website.
Microsoft Windows - addressed in versions 10 1607 10.0.14393.9339, 10 1809 10.0.17763.9020, 11 26H1 10.0.28000.2525
Windows Server - addressed in versions 2012 R2 6.3.9600.23291, 2012 6.2.9200.26226, 2016 10.0.14393.9339, 2019 10.0.17763.9020, 2022 10.0.20348.5386, 2025 10.0.26100.33158
Windows Server - addressed in versions 2012 R2 6.3.9600.23291, 2012 6.2.9200.26226, 2016 10.0.14393.9339, 2019 10.0.17763.9020, 2022 10.0.20348.5386, 2025 10.0.26100.33158