CVEs / CVE-2026-56155
CVE-2026-56155: Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability
- Known exploited in the CISA KEV catalog since 14 Jul 2026
- high 7.8 CVSS 3.1 (from the CNA)
- EPSS 0.34% chance of exploitation in the next 30 days, higher than 28% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Active Directory Federation Services contains an insufficient granularity of access control vulnerability that allows an authorized attacker to elevate privileges locally.
Description
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Windows 10 Version 1607 | from 10.0.14393.0, before 10.0.14393.9339 | 10.0.14393.9339 |
| Microsoft Windows 10 Version 1809 | from 10.0.17763.0, before 10.0.17763.9020 | 10.0.17763.9020 |
| Microsoft Windows Server 2012 | from 6.2.9200.0, before 6.2.9200.26226 | 6.2.9200.26226 |
| Microsoft Windows Server 2012 (Server Core installation) | from 6.2.9200.0, before 6.2.9200.26226 | 6.2.9200.26226 |
| Microsoft Windows Server 2012 R2 | from 6.3.9600.0, before 6.3.9600.23291 | 6.3.9600.23291 |
| Microsoft Windows Server 2012 R2 (Server Core installation) | from 6.3.9600.0, before 6.3.9600.23291 | 6.3.9600.23291 |
| Microsoft Windows Server 2016 | from 10.0.14393.0, before 10.0.14393.9339 | 10.0.14393.9339 |
| Microsoft Windows Server 2016 (Server Core installation) | from 10.0.14393.0, before 10.0.14393.9339 | 10.0.14393.9339 |
| Microsoft Windows Server 2019 | from 10.0.17763.0, before 10.0.17763.9020 | 10.0.17763.9020 |
| Microsoft Windows Server 2019 (Server Core installation) | from 10.0.17763.0, before 10.0.17763.9020 | 10.0.17763.9020 |
| Microsoft Windows Server 2022 | from 10.0.20348.0, before 10.0.20348.5386 | 10.0.20348.5386 |
| Microsoft Windows Server 2025 | from 10.0.26100.0, before 10.0.26100.33158 | 10.0.26100.33158 |
| Microsoft Windows Server 2025 (Server Core installation) | from 10.0.26100.0, before 10.0.26100.33158 | 10.0.26100.33158 |
Exploitation
| In CISA KEV since | 14 Jul 2026 |
|---|---|
| Due date for US federal agencies | 28 Jul 2026 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 7.8 highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-1220 |
References
- CVE-2026-56155 on NVD
- CVE-2026-56155 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-56155 (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- https://learn.microsoft.com/en-us/windows-server/identity/ad-fs/decommission/adfs-decommission-guide (cited by CISA)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56155 Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56155 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.