CVE-2026-56155: Microsoft AD FS privilege escalation via insufficient access control granularity

CVE-2026-56155 · Severity: critical · CVSS 7.8 · Exploited in the wild · Published 2026-07-14

Microsoft Active Directory Federation Services (AD FS), a component used to manage single sign-on and identity access across different applications, contains a security flaw. This vulnerability allows an attacker who already has basic access to a system to gain higher-level administrative privileges. If exploited, this could allow an unauthorized user to take full control of the identity management server, potentially compromising user credentials and corporate data.

Technologies: Microsoft Active Directory Federation Services, Microsoft Windows Server 2012 R2, Microsoft Windows 10, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019. Vendors: Microsoft.

Quick answers

Is CVE-2026-56155 exploited in the wild?
Yes. CVE-2026-56155 is known to be exploited in the wild, first recorded on 14 July 2026. Treat it as urgent.
How severe is CVE-2026-56155?
Critical severity, with a CVSS score of 7.8, published 14 July 2026.
Which products and versions are affected?
Microsoft Active Directory Federation Services Windows 10, Windows Server 2012, 2012 R2, 2016, 2019; Microsoft Windows Server 2012 R2 < 6.3.9600.23291; Microsoft Windows 10 < 10.0.14393.9339; Microsoft Windows Server 2012 < 6.2.9200.26226; and 2 more.
Is there a fix for CVE-2026-56155?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-56155 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-56155?
Check whether you run Microsoft Active Directory Federation Services, Microsoft Windows Server 2012 R2, Microsoft Windows 10 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A privilege escalation vulnerability exists in Microsoft Active Directory Federation Services (AD FS) due to insufficient granularity of access control (CWE-1220). An attacker with local access and low-level privileges can exploit this flaw to gain elevated system permissions. The attack vector is local, requiring the attacker to already have an authorized account on the target system. Successful exploitation could lead to a complete compromise of the AD FS server, impacting confidentiality, integrity, and availability. Microsoft has released updates to address this issue across various Windows and Windows Server versions.

Affected products

  • Microsoft Active Directory Federation Services (AD FS) Windows 10, Windows Server 2012, 2012 R2, 2016, 2019

Timeline

  • 2026-07-14: disclosed
  • 2026-07-14: advisory

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