CVE-2017-0159 in Windows
Summary
by MITRE
A security feature bypass vulnerability exists in Windows 10 1607, Windows Server 2012 R2, and Windows 2016 when ADFS incorrectly treats requests coming from Extranet clients as Intranet requests, aka "ADFS Security Feature Bypass Vulnerability."
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Analysis
by VulDB Data Team • 06/05/2020
The CVE-2017-0159 vulnerability represents a critical security feature bypass affecting Microsoft Active Directory Federation Services implementations across multiple Windows operating systems including Windows 10 version 1607, Windows Server 2012 R2, and Windows Server 2016. This vulnerability stems from a fundamental misclassification error within the ADFS authentication framework where the system incorrectly processes authentication requests from extranet clients, treating them as if they originated from internal network sources. The flaw specifically impacts the authentication and authorization mechanisms that rely on network location detection to enforce security policies, creating a scenario where external users can potentially bypass certain security controls that should only be accessible to internal network entities. This misclassification occurs at the protocol level during the authentication handshake process, where ADFS fails to properly validate the true network origin of incoming requests, allowing malicious actors to exploit this gap in trust verification.
The technical implementation of this vulnerability exploits the inherent trust relationships within ADFS infrastructure by manipulating network location detection mechanisms that are critical for enforcing security policies. When ADFS receives authentication requests, it performs a series of checks to determine whether the request originates from an internal or external network segment. The vulnerability occurs when the system incorrectly identifies extranet clients as internal network entities, thereby granting them access to resources and authentication mechanisms that should be restricted to legitimate internal users. This misclassification allows attackers to bypass security controls that are typically enforced based on network location, potentially enabling unauthorized access to protected resources, privilege escalation, and unauthorized data access. The flaw operates at the application layer and affects the authentication protocol handling within Microsoft's federation services implementation.
The operational impact of CVE-2017-0159 extends beyond simple authentication bypass scenarios and represents a significant risk to enterprise security infrastructure. Organizations utilizing ADFS for federated identity management face potential compromise of their entire authentication ecosystem when this vulnerability is exploited, as attackers can leverage the bypass to gain access to sensitive corporate resources without proper authorization. The vulnerability creates a persistent risk that can be exploited by attackers who have already gained initial access to the network, allowing them to escalate privileges and move laterally within the organization's infrastructure. This security gap undermines the fundamental trust model that ADFS relies upon for secure authentication, potentially enabling attackers to impersonate legitimate users, access restricted applications, and compromise sensitive data repositories. The impact is particularly severe in environments where ADFS is used for single sign-on operations and cross-domain authentication scenarios.
Mitigation strategies for CVE-2017-0159 require immediate implementation of Microsoft security patches and updates, specifically targeting the identified ADFS vulnerability in the affected Windows versions. Organizations should implement network segmentation controls to limit direct access to ADFS servers from external networks and establish additional authentication layers that do not rely solely on network location detection. Security administrators should conduct comprehensive audits of their ADFS configurations to identify and correct any misconfigurations that could exacerbate the vulnerability. The implementation of multi-factor authentication and additional verification mechanisms should be prioritized to reduce the risk associated with this bypass vulnerability. Organizations should also monitor authentication logs for unusual patterns that might indicate exploitation attempts and implement network-based intrusion detection systems to identify potential abuse of this vulnerability. This vulnerability aligns with CWE-284 Access Control Issues and maps to ATT&CK technique T1078 Valid Accounts for privilege escalation and lateral movement activities.
The vulnerability demonstrates the critical importance of proper authentication protocol implementation and the risks associated with relying on network location for security decisions. Organizations should recognize that modern security architectures must not depend solely on network segmentation for access control, as this approach creates exploitable gaps when network location detection fails. The flaw underscores the need for defense-in-depth strategies that combine multiple security controls rather than relying on single points of failure. Security professionals should consider implementing additional monitoring and alerting mechanisms specifically designed to detect anomalous authentication patterns that might indicate exploitation of this vulnerability. Regular security assessments and penetration testing of federation services should be conducted to identify similar implementation flaws that could create comparable security risks. This vulnerability serves as a reminder that even seemingly minor misconfigurations in core security services can create substantial risks to enterprise security infrastructure.