CVE-2026-56155
Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 28 July 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.35% probability · 28th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 14 July 2026 · due 28 July 2026
- Weakness
- CWE-1220
- Affected
- microsoft/windows 10 1607 · microsoft/windows 10 1809 · microsoft/windows server 2012 · microsoft/windows server 2016 · microsoft/windows server 2019 · microsoft/windows server 2022 · microsoft/windows server 2025
- Source
- secure@microsoft.com
EPSS 0.3% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
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. 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
References
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.