CVE-2026-56155: Active Directory Federation Services Elevation of Privilege Vulnerability

Overview

Severity

High (CVSS 7.8)

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

Category

Elevation of Privilege

Exploit Status

Actively Exploited

Exploitation Likelihood

Detected

Patch Tuesday

2026-Jul

Released

2026-07-14

EPSS Score

0.38% (percentile: 30.1%)

CISA KEV

Listed — due 2026-07-28

Description

Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.

FAQ

What privileges could be gained by an attacker who successfully exploited the vulnerability? An attacker who successfully exploited this vulnerability could gain administrator privileges.

Affected Products (15)

Windows

• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2025 (Server Core installation)
• Windows Server 2025
• Windows 10 Version 1607 for 32-bit Systems
• Windows 10 Version 1607 for x64-based Systems
• Windows Server 2016
• Windows Server 2016 (Server Core installation)

ESU

• Windows Server 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Security Updates (6)

• 5099538
• 5099540
• 5099536
• 5099535
• 5099445
• 5099444

Acknowledgments

Scott Clark (DART) with <a href="https://www.microsoft.com/">Microsoft</a>, Jeremy Kingston (DART) with <a href="https://www.microsoft.com/">Microsoft</a>

Revision History

• 2026-07-14: Information published.