CVE-2018-8340 in Windows
Summary
by MITRE
A security feature bypass vulnerability exists when Active Directory Federation Services (AD FS) improperly handles multi-factor authentication requests, aka "AD FS Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows Server 2012 R2, Windows 10 Servers.
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Analysis
by VulDB Data Team • 05/01/2023
The CVE-2018-8340 vulnerability represents a critical security feature bypass in Active Directory Federation Services that undermines the integrity of multi-factor authentication mechanisms. This flaw specifically targets the authentication processing logic within AD FS components, creating a pathway for unauthorized access that circumvents the intended security controls. The vulnerability affects multiple Microsoft server operating systems including Windows Server 2016, Windows Server 2012 R2, and Windows 10 Servers, making it a widespread concern for enterprise environments that rely on federated identity solutions. The issue stems from how AD FS handles authentication requests when multi-factor authentication is required, allowing attackers to bypass the additional security layers that should be enforced during the authentication process.
The technical implementation of this vulnerability resides in the improper validation and handling of authentication tokens within the AD FS infrastructure. When legitimate authentication requests are processed, the system fails to properly validate the multi-factor authentication state, enabling attackers to manipulate the authentication flow and present valid credentials without completing the required secondary authentication factors. This flaw operates at the protocol level within the AD FS authentication pipeline, specifically affecting the claims processing and token generation mechanisms that are fundamental to federated identity management. The vulnerability can be exploited through crafted authentication requests that manipulate the authentication context, effectively allowing an attacker to authenticate as any user within the system without satisfying the multi-factor authentication requirements.
The operational impact of CVE-2018-8340 extends beyond simple unauthorized access to create significant risks for enterprise security postures. Organizations utilizing AD FS for single sign-on solutions face potential compromise of their entire federated identity ecosystem, as attackers can exploit this vulnerability to gain access to sensitive applications and systems that should require additional authentication factors. The security implications are particularly severe for environments where AD FS is used to protect privileged accounts or systems containing sensitive data, as the bypass allows for elevation of privileges and lateral movement within the network. This vulnerability directly impacts the principle of least privilege and can lead to complete system compromise when combined with other exploitation techniques.
Mitigation strategies for this vulnerability should focus on immediate patch deployment through Microsoft's security updates, as the primary fix involves correcting the authentication validation logic within AD FS components. Organizations should also implement network segmentation to limit access to AD FS servers, employ additional monitoring for anomalous authentication patterns, and consider implementing supplementary authentication controls such as conditional access policies. The vulnerability aligns with CWE-284, which addresses improper access control in authentication systems, and maps to ATT&CK technique T1078 for valid accounts and T1531 for credential manipulation. Security teams should conduct comprehensive assessments of their AD FS implementations to identify potential exploitation vectors and implement continuous monitoring to detect unauthorized authentication attempts that may indicate exploitation of this vulnerability.