CVE-2026-56155 in Windows
Summary
by MITRE • 07/14/2026
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 07/14/2026
Active Directory Federation Services represents a critical component in enterprise identity management, serving as a bridge between on-premises directories and cloud-based applications through federated identity protocols. The vulnerability stems from insufficient granularity in access control mechanisms within AD FS implementations, creating opportunities for privilege escalation attacks that can compromise entire organizational security postures. This weakness specifically manifests when the system fails to properly enforce least-privilege principles during authentication and authorization processes, allowing attackers who have gained initial access to potentially escalate their privileges locally through manipulated federation claims or improperly configured trust relationships.
The technical flaw exploits fundamental weaknesses in how AD FS handles access control decisions, particularly when processing security tokens and claims that define user permissions within federated environments. Attackers can manipulate the flow of identity information by crafting specially crafted authentication requests or modifying existing claims to gain elevated access rights within the system. This vulnerability typically arises from misconfigurations in trust relationships between AD FS servers and relying party applications, where insufficient validation occurs during token processing stages. The lack of proper access control granularity means that legitimate users with limited permissions might be granted broader access than intended, while attackers can exploit these gaps to move laterally within the network or escalate their privileges beyond what should be permitted under normal operational procedures.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally undermines the security model of federated identity systems and creates persistent attack vectors that can remain undetected for extended periods. Organizations using AD FS implementations may experience unauthorized access to sensitive data, system compromise, and potential lateral movement throughout their network infrastructure. The vulnerability is particularly dangerous because it operates at the intersection of authentication and authorization processes, making detection challenging for traditional security monitoring systems that focus on network-level activities rather than identity-based access control violations. This weakness can enable attackers to maintain persistent access while avoiding standard security controls designed to prevent privilege escalation, as evidenced by various attack patterns documented in cybersecurity threat intelligence reports.
Effective mitigation strategies must address both the immediate configuration issues and implement comprehensive monitoring solutions to detect anomalous access patterns within federated environments. Organizations should enforce strict access control policies through proper configuration of AD FS trust relationships, implement robust claims rule configurations, and establish continuous monitoring of authentication events for suspicious privilege escalation activities. Security controls should include regular auditing of AD FS configurations against established security benchmarks such as those provided by the Center for Internet Security or NIST guidelines, with particular attention to implementing principle of least privilege across all federated identity scenarios. Additionally, organizations must ensure that their security operations centers maintain visibility into federation-related activities through proper logging and alerting mechanisms, as this vulnerability often operates below the radar of standard network security monitoring tools due to its focus on identity management rather than traditional network traffic analysis. The implementation of multi-factor authentication for privileged AD FS access and regular penetration testing of federated environments can further reduce the risk exposure associated with these access control weaknesses.