CVE-2018-0890 in Windows
Summary
by MITRE
A security feature bypass vulnerability exists when Active Directory incorrectly applies Network Isolation settings, aka "Active Directory Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows 10, Windows 10 Servers.
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Analysis
by VulDB Data Team • 02/09/2021
The vulnerability described in CVE-2018-0890 represents a critical security feature bypass in Microsoft Active Directory implementations that undermines fundamental network isolation controls. This flaw specifically targets the Network Isolation settings within Active Directory, which are designed to enforce strict access controls and prevent unauthorized network communications between different security zones. The vulnerability allows attackers to circumvent these protective measures, potentially enabling lateral movement and privilege escalation within targeted environments. The issue affects multiple Windows Server and client operating systems including Windows Server 2016 and various Windows 10 versions, making it particularly concerning given the widespread deployment of these platforms in enterprise environments.
The technical root cause of this vulnerability stems from how Active Directory processes and applies Network Isolation policies when handling network traffic and authentication requests. When Active Directory incorrectly evaluates network isolation settings, it fails to properly enforce the security boundaries that should separate different network segments or security domains. This misapplication allows malicious actors to bypass the intended network segmentation controls that would normally prevent direct communication between isolated network zones. The flaw operates at the protocol level where network isolation policies are supposed to be enforced, creating a pathway for unauthorized access that should have been blocked by the security infrastructure. This behavior aligns with CWE-693, which describes security feature bypass vulnerabilities where protective mechanisms fail to properly enforce their intended security controls.
The operational impact of this vulnerability extends beyond simple network access issues, creating significant risks for enterprise security postures. Attackers who successfully exploit this vulnerability can potentially move laterally within networks that rely on Active Directory for authentication and authorization, undermining the security model that organizations depend upon for protecting sensitive data and systems. The bypass allows for unauthorized communication between network segments that should remain isolated, potentially enabling attackers to access systems that are normally protected by network segmentation policies. This vulnerability particularly affects environments where Active Directory is used as the primary authentication and authorization service, as it undermines the trust model that underpins these security controls. The attack surface is further expanded because the vulnerability affects both server and client operating systems, meaning that compromise of any single system within the domain could potentially enable broader network access.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security updates and patches that address the Network Isolation implementation issues in Active Directory. Security administrators should also conduct thorough reviews of their current network segmentation policies and validate that existing network isolation controls are functioning properly. Monitoring for unusual network communication patterns between isolated segments and implementing additional intrusion detection measures can help identify potential exploitation attempts. The vulnerability demonstrates the critical importance of proper security feature implementation and enforcement within enterprise authentication systems, as failures in these controls can have cascading effects throughout the entire security infrastructure. Organizations should consider implementing additional layers of security controls beyond network segmentation to protect against potential exploitation of this type of vulnerability, as outlined in the ATT&CK framework's lateral movement tactics that specifically target authentication and authorization systems.