CVE-2026-83674 in Windows
Summary
by MITRE • 10/14/2026
Weak authentication in Active Directory Federation Services (AD FS) allows an unauthorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 10/14/2026
Active Directory Federation Services serves as a critical component in modern enterprise identity management architectures, facilitating single sign-on and secure cross-organization trust relationships through the implementation of security token services. The protocol relies heavily on cryptographic mechanisms to ensure that authentication assertions issued by an Identity Provider are authentic and have not been tampered with during transit or storage. When weak authentication configurations exist within this framework, it fundamentally undermines the integrity of these trust boundaries. Specifically, vulnerabilities related to improper validation of digital signatures or reliance on deprecated hashing algorithms can allow malicious actors to bypass standard verification processes that are designed to prevent identity spoofing and session hijacking.
The technical flaw typically stems from a failure to strictly enforce signature validation requirements for incoming security tokens, particularly in scenarios involving SAML assertions or WS-Federation requests. An attacker positioned within the network path or possessing access to compromised credentials can exploit this weakness by crafting forged authentication responses that mimic legitimate identity providers. By manipulating the XML structure of these tokens and omitting or altering digital signatures where they are not strictly validated against a trusted certificate store, the adversary can inject false user identities into the system. This manipulation allows the attacker to assume the privileges associated with any targeted account without possessing valid credentials for that specific user, effectively bypassing multi-factor authentication controls if those controls rely on token integrity rather than independent verification steps.
The operational impact of such a vulnerability is severe and far-reaching within an organization's security posture. Successful exploitation enables unauthorized access to sensitive applications, databases, and cloud services protected by the federation service. This can lead to data exfiltration, lateral movement across internal networks, and potential compromise of privileged administrative accounts if they are accessible through federated trust relationships. Furthermore, because AD FS often acts as a gateway for hybrid identity scenarios connecting on-premises Active Directory with Azure AD or other cloud services, the breach extends beyond local infrastructure into cloud environments, complicating incident response efforts due to the distributed nature of the compromised identities and logs.
From an industry standard perspective, this vulnerability aligns closely with CWE-287 Improper Authentication, where the system fails to adequately verify identity before granting access. It also relates to CWE-345 Insufficient Verification of Data Authenticity, as the core issue lies in the acceptance of unverified or weakly verified security tokens. In terms of tactical mapping within the MITRE ATT&CK framework, this behavior corresponds to T1078 Valid Accounts and potentially T1621 Multi-Factor Authentication Request Interception if the attack vector involves intercepting and manipulating authentication flows. The exploitation technique often falls under T1556 Modifying Authentication Process or T1553 Subvert Trust Controls when the attacker manipulates certificate validation logic to establish a false sense of trust with the federation service.
Mitigation strategies must focus on hardening the configuration of Active Directory Federation Services and enforcing strict cryptographic standards. Administrators should ensure that all incoming tokens are validated against trusted root certificates using strong hashing algorithms such as SHA-256 or higher, explicitly disabling support for legacy protocols like NTLMv1 if they remain enabled in any capacity. It is essential to configure the federation service to reject SAML assertions that lack valid digital signatures unless there is a specific business requirement and compensating controls are in place. Regular auditing of trust relationships ensures that only authorized identity providers can issue tokens, reducing the attack surface for spoofing attempts. Additionally, implementing network segmentation limits an attacker's ability to perform man-in-the-middle attacks against federation traffic, while monitoring tools should be configured to detect anomalous patterns such as repeated authentication failures or token validation errors indicative of exploitation attempts.