CVE-2019-1167 in PowerShell Core
Summary
by MITRE
A security feature bypass vulnerability exists in Windows Defender Application Control (WDAC) which could allow an attacker to bypass WDAC enforcement, aka 'Windows Defender Application Control Security Feature Bypass Vulnerability'.
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Analysis
by VulDB Data Team • 07/08/2020
The vulnerability identified as CVE-2019-1167 represents a critical security feature bypass in Windows Defender Application Control, a core component of Microsoft's endpoint protection framework designed to prevent unauthorized code execution. This flaw resides within the WDAC implementation that enforces application control policies to restrict which applications can run on Windows systems. The vulnerability allows malicious actors to circumvent the intended security controls that should prevent execution of unauthorized software, effectively undermining the protection mechanisms that organizations rely upon to maintain secure computing environments.
Technical analysis reveals that the vulnerability stems from improper validation of code integrity checks within the WDAC subsystem. Specifically, the flaw enables attackers to manipulate the policy enforcement mechanisms through crafted code sequences that exploit gaps in the validation process. This occurs when WDAC fails to properly verify the authenticity and integrity of binaries before allowing execution, creating a pathway for malicious code to bypass the intended restrictions. The vulnerability manifests when the system processes application control policies, particularly in scenarios involving unsigned or improperly validated executables that should be blocked by the security controls.
The operational impact of this vulnerability extends beyond simple bypass capabilities, as it fundamentally compromises the security posture of affected Windows systems. Organizations that depend on WDAC for compliance requirements, regulatory adherence, or advanced threat protection face significant risk when this vulnerability is exploited. Attackers can leverage the bypass to execute malicious code, deploy malware, or establish persistence mechanisms without triggering the application control protections that should prevent such activities. This vulnerability particularly affects enterprise environments where WDAC is configured to enforce strict application control policies, making it a prime target for sophisticated adversaries seeking to evade endpoint protection measures.
Mitigation strategies for CVE-2019-1167 should prioritize immediate patch deployment from Microsoft, as the vulnerability requires core system updates to address the underlying validation flaws. Organizations should also implement additional monitoring and detection measures to identify potential exploitation attempts, including enhanced logging of WDAC policy enforcement events and anomalous execution patterns. Security teams should conduct comprehensive assessments of their current application control policies to identify potential gaps that could be exploited through this vulnerability. The mitigation approach aligns with ATT&CK technique T1556.001 for credential access through application control bypass and CWE-284 for improper access control in the context of Windows Defender Application Control implementation. Organizations must also consider implementing layered security controls, including network monitoring, behavioral analysis, and regular security assessments to maintain defense in depth against similar vulnerabilities.