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CVE-2026-56155: Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-07-14
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-14 · updated 2026-07-15
• Weakness: CWE-1220

Description

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

Affected products

• Microsoft Windows 10 1607: before 10.0.14393.9339 — fixed in 10.0.14393.9339
• Microsoft Windows 10: before 10.0.17763.9020 — fixed in 10.0.17763.9020
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: before 10.0.14393.9339 — fixed in 10.0.14393.9339
• Microsoft Windows Server 2019: before 10.0.17763.9020 — fixed in 10.0.17763.9020
• Microsoft Windows Server 2022: before 10.0.20348.5386 — fixed in 10.0.20348.5386
• Microsoft Windows Server 2025: before 10.0.26100.33158 — fixed in 10.0.26100.33158

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.9339; Microsoft Windows 10 10.0.17763.9020; Microsoft Windows Server 2016 10.0.14393.9339; Microsoft Windows Server 2019 10.0.17763.9020; Microsoft Windows Server 2022 10.0.20348.5386; Microsoft Windows Server 2025 10.0.26100.33158. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56155
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56155

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