Microsoft Active Directory Federation Services
Microsoft Active Directory Federation Services is affected by a high-severity vulnerability (CVE-2026-56155) that is confirmed to be actively exploited in the wild. 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.
What is this vulnerability?
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
How it works
This is classified as CWE-1220. In plain terms, an attacker could use this flaw in Active Directory Federation Services to gain access, disrupt service, or steal data — the exact impact depends on how it’s deployed in your environment.
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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.
Mitigations
- Apply the vendor’s security patch or update as soon as it’s available and tested.
- If no patch exists yet, apply the vendor’s temporary workaround.
- Limit network exposure of the affected system until it’s patched.
- Review logs for signs of prior exploitation, especially if it’s flagged for ransomware use.
Recommendations
- Confirm whether Microsoft Active Directory Federation Services is used anywhere in your environment.
- Patch internet-facing systems first, then internal ones.
- Set a reminder ahead of the remediation deadline so it doesn’t slip.
- Subscribe to the vendor’s security advisories for earlier warning next time.
Compiled from public threat intelligence (CISA Known Exploited Vulnerabilities catalog and the National Vulnerability Database, referenced in 2 public advisories).