Access Control Flaw in Active Directory Federation Services by Microsoft

CVE-2026-56155

What is CVE-2026-56155?

CVE-2026-56155 is a security vulnerability identified in Microsoft’s Active Directory Federation Services (AD FS), a component widely used in enterprise environments to provide single sign-on and federated identity management capabilities. This specific vulnerability relates to an insufficient granularity of access control within AD FS, which allows an authorized attacker with access to potentially elevate their privileges locally. Such privilege escalation can lead to unauthorized access to sensitive data and critical infrastructure, compromising the integrity and confidentiality of organizational systems. The technical details suggest that, while the attacker may not be entirely outside the organization, their existing access can be exploited, making the issue particularly severe as it bypasses conventional perimeter defenses.

Potential impact of CVE-2026-56155

1. Privilege Escalation: The primary impact of CVE-2026-56155 is that it enables attackers who already have some level of authorization to escalate their privileges. This can allow them to gain control over sensitive data and system functions that should be restricted, leading to potential data breaches and unauthorized actions within the system.

2. Data Breaches and Information Theft: With elevated privileges, attackers can access sensitive databases and files, leading to the possibility of leaking confidential information. This can have severe implications for organizations, including loss of intellectual property and violation of data protection regulations.

3. Increased Risk of Malware Infection: The vulnerability increases the likelihood of further exploitation. Once an attacker gains elevated privileges, they can install malware or additional exploits within the network, leading to broader system compromise, including the potential for ransomware deployment. The flexibility to maneuver within the network enhances the adversary’s capability to carry out extensive malicious activities.

References