Insufficient granularity of access control in Windows and Windows Server - CVE-2026-56155
Published: July 14, 2026
Vulnerability identifier: #VU137539
CSH Severity: High
CVSS v4.0: 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/E:A/U:Amber
CVE-ID: CVE-2026-56155
CWE-ID: CWE-1220
Exploitation vector: Local access
Exploit availability:
The vulnerability is being exploited in the wild
Vendor: Microsoft
Affected software:
Windows
Windows Server
Windows
Windows Server
Detailed vulnerability description
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.
How to mitigate CVE-2026-56155
Install updates from vendor's website.