CVE-2026-50647 in Windows
Summary
by MITRE • 07/14/2026
Loop with unreachable exit condition ('infinite loop') in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 07/14/2026
Active Directory Federation Services represents a critical component in enterprise identity management systems, providing single sign-on capabilities and federated authentication services across organizations. The vulnerability manifests as an infinite loop condition within the AD FS implementation that occurs when processing specific authentication requests. This flaw exists in the service's handling of certain token validation sequences where the loop structure lacks proper exit conditions, causing the authentication process to enter a continuous iteration state. When exploited by an unauthenticated attacker, this vulnerability enables denial-of-service attacks against the federation service, effectively preventing legitimate users from accessing federated resources and applications that depend on AD FS for authentication.
The technical implementation of this vulnerability stems from inadequate boundary checking within the token processing logic of AD FS servers. The loop structures responsible for validating security tokens contain flawed conditional statements that fail to account for all possible input states, creating scenarios where the iteration continues indefinitely without proper termination. This condition typically occurs during the processing of malformed or specially crafted SAML assertions or OAuth tokens that trigger the problematic code path. The vulnerability aligns with CWE-835 which specifically addresses infinite loops due to missing loop exit conditions, representing a classic software engineering flaw that directly impacts system availability.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the entire federated authentication ecosystem. Organizations relying on AD FS for identity federation face potential business continuity issues when attackers exploit this weakness, particularly in environments where users depend on seamless access to cloud applications and internal resources through single sign-on mechanisms. The attack vector requires minimal privileges since the flaw exists in the authentication service itself rather than requiring elevated access or specific user credentials. Network-based exploitation allows attackers to consume system resources continuously, leading to performance degradation and complete service unavailability for legitimate users attempting to authenticate.
Mitigation strategies should focus on immediate patch application from Microsoft as part of regular security maintenance procedures, along with network-level monitoring to detect anomalous authentication request patterns that may indicate exploitation attempts. Organizations should implement rate limiting mechanisms at the perimeter to prevent abuse of the vulnerable authentication endpoints while maintaining visibility into authentication flows through enhanced logging and alerting systems. The implementation of redundant authentication services and failover mechanisms can provide resilience against such attacks, ensuring continued access to critical applications during incident response activities. Additionally, security teams should conduct regular vulnerability assessments targeting federation services and maintain updated threat intelligence feeds that specifically monitor for exploitation attempts related to AD FS vulnerabilities. This approach aligns with ATT&CK technique T1499 which covers network denial-of-service attacks and emphasizes the importance of protecting authentication infrastructure from availability-based threats.