---
id: "CVE-2026-56155"
kind: "vulnerability"
aliases: ["CVE-2026-56155"]
title: "Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized\u2026"
severity: "high"
cvss: 7.8
epss: null
exploited: true
status: "open"
category: "vendor"
products: [{"name": "Microsoft Active Directory Federation Services", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1607", "fixed": ["10.0.14393.9339"], "affected": "< 10.0.14393.9339", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1809", "fixed": ["10.0.17763.9020"], "affected": "< 10.0.17763.9020", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "= r2", "ecosystem": "vendor"}, {"name": "microsoft windows server 2016", "fixed": ["10.0.14393.9339"], "affected": "< 10.0.14393.9339", "ecosystem": "vendor"}, {"name": "microsoft windows server 2019", "fixed": ["10.0.17763.9020"], "affected": "< 10.0.17763.9020", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022", "fixed": ["10.0.20348.5386"], "affected": "< 10.0.20348.5386", "ecosystem": "vendor"}, {"name": "microsoft windows server 2025", "fixed": ["10.0.26100.33158"], "affected": "< 10.0.26100.33158", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["active-directory-federation-services", "exploited", "microsoft", "vendor", "windows-server"]
not_affected_if: ["no-adfs-deployment"]
published_at: "2026-07-14T00:00:00+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T23:44:51+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-56155", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56155", "first_seen_at": "2026-10-23T23:44:51+00:00"}]
---

# Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized…

Microsoft Active Directory Federation Services has an access control flaw that lets an authorized local user elevate their privileges. CISA lists it as actively exploited in the wild.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft Active Directory Federation Services affected ? fixed ?
- vendor:microsoft windows 10 1607 affected < 10.0.14393.9339 fixed 10.0.14393.9339
- vendor:microsoft windows 10 1809 affected < 10.0.17763.9020 fixed 10.0.17763.9020
- vendor:microsoft windows server 2012 affected ? fixed ?
- vendor:microsoft windows server 2012 affected = r2 fixed ?
- vendor:microsoft windows server 2016 affected < 10.0.14393.9339 fixed 10.0.14393.9339
- vendor:microsoft windows server 2019 affected < 10.0.17763.9020 fixed 10.0.17763.9020
- vendor:microsoft windows server 2022 affected < 10.0.20348.5386 fixed 10.0.20348.5386
- vendor:microsoft windows server 2025 affected < 10.0.26100.33158 fixed 10.0.26100.33158

## Fix

Apply the mitigations and patches from Microsoft's advisory for CVE-2026-56155, following CISA BOD 26-04 guidance; discontinue use of the product if mitigations are unavailable.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-56155
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-56155

## From the sources

Microsoft Active Directory Federation Services contains an insufficient granularity of access control vulnerability that allows an authorized attacker to elevate privileges locally.

CISA 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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_