CVE-2026-56155

Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Required action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

CISA notes
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-56155 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-56155; https://learn.microsoft.com/en-us/windows-server/identity/ad-fs/decommission/adfs-decommission-guide