CVE-2019-0631 in Windows
Summary
by MITRE
A security feature bypass vulnerability exists in Windows which could allow an attacker to bypass Device Guard, aka 'Windows Security Feature Bypass Vulnerability'. This CVE ID is unique from CVE-2019-0627, CVE-2019-0632.
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Analysis
by VulDB Data Team • 07/13/2024
The vulnerability identified as CVE-2019-0631 represents a critical security feature bypass in Microsoft Windows operating systems that specifically targets Device Guard implementation. Device Guard serves as a crucial security mechanism designed to prevent unauthorized code execution by enforcing strict policies that control which applications and scripts can run on a system. This vulnerability allows attackers to circumvent these protective measures, effectively undermining the core security posture of affected Windows environments. The flaw exists within the Windows kernel and user-mode components that handle Device Guard policy enforcement, creating an exploitable path that adversaries can leverage to execute malicious code without triggering the intended security controls.
The technical implementation of this vulnerability stems from improper validation of code integrity checks within the Windows kernel. When Device Guard evaluates code for execution, it relies on cryptographic signatures and policy enforcement mechanisms to verify authenticity and compliance with established security policies. However, CVE-2019-0631 exploits a weakness in how these validation processes handle certain code patterns, allowing malicious payloads to be marked as trusted even when they fail standard integrity checks. This flaw operates at the intersection of kernel-mode and user-mode security components, specifically affecting the Windows Defender Application Control (WDAC) framework that underpins Device Guard functionality. The vulnerability manifests when the system processes code that should be blocked by Device Guard policies, but due to the flawed validation logic, the system incorrectly permits execution.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally compromises the integrity of endpoint security measures that organizations rely upon for protection against advanced persistent threats. Attackers can leverage this vulnerability to bypass not only Device Guard but also related security controls such as Windows Defender Application Control, which provides a baseline of protection against malicious software execution. The vulnerability affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, creating widespread exposure across enterprise environments where Device Guard is enabled as part of security configurations. Organizations that have implemented Device Guard as a defense-in-depth strategy find their investments undermined by this bypass mechanism, as it allows attackers to execute arbitrary code without triggering the security controls that should prevent such activities.
Security researchers have classified this vulnerability according to CWE-284, which addresses improper access control mechanisms, and it aligns with ATT&CK technique T1556.200 related to credential access through Windows Remote Management. The vulnerability's exploitation typically involves crafting malicious code that can bypass the Device Guard policy enforcement by exploiting specific conditions in how kernel components validate code signatures. Mitigation efforts focus on applying Microsoft's security patches that address the underlying validation logic flaws, while organizations should also implement additional monitoring for anomalous code execution patterns that might indicate exploitation attempts. Network administrators should consider implementing additional endpoint detection and response measures to identify potential exploitation attempts, as traditional signature-based detection may not be sufficient against this type of vulnerability. The incident highlights the critical importance of maintaining up-to-date security patches and demonstrates how even well-designed security features can be undermined by subtle implementation flaws in kernel components.