CVE-2018-8492 in Windows
Summary
by MITRE
A security feature bypass vulnerability exists in Device Guard that could allow an attacker to inject malicious code into a Windows PowerShell session, aka "Device Guard Code Integrity Policy Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows 10, Windows Server 2019, Windows 10 Servers.
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Analysis
by VulDB Data Team • 05/23/2023
The CVE-2018-8492 vulnerability represents a critical security feature bypass in Microsoft's Device Guard implementation, which is designed to enforce code integrity policies and prevent unauthorized code execution. This flaw specifically targets the code integrity policy enforcement mechanisms that are fundamental to Windows security architecture, particularly within PowerShell sessions where malicious code injection could occur. The vulnerability exists in multiple Windows versions including Windows Server 2016, Windows 10, Windows Server 2019, and Windows 10 Servers, indicating a widespread impact across Microsoft's enterprise and server operating systems. Device Guard serves as a crucial defense mechanism that restricts which code can execute on a system by enforcing policies that define trusted applications and scripts, making this bypass particularly concerning for enterprise security.
The technical nature of this vulnerability stems from an insufficient validation mechanism within Device Guard's code integrity policy enforcement. Attackers can exploit this weakness to bypass the security controls that normally prevent malicious PowerShell scripts from executing, allowing them to inject and run unauthorized code within PowerShell sessions. The flaw essentially allows threat actors to circumvent the intended security boundaries that Device Guard is designed to maintain, effectively undermining the principle of least privilege and code integrity enforcement. This bypass occurs at the policy enforcement level where Device Guard should be strictly validating code signatures and execution policies, but instead permits malicious code to proceed through the validation process. The vulnerability specifically affects PowerShell sessions, which are commonly used by administrators and attackers alike, making it particularly dangerous in enterprise environments where PowerShell is extensively utilized for system administration tasks.
The operational impact of CVE-2018-8492 is severe and multifaceted, as it enables attackers to execute arbitrary code within PowerShell environments without proper authorization. This capability significantly expands an attacker's exploitation surface and can lead to complete system compromise, lateral movement within networks, and persistence mechanisms. The vulnerability allows for privilege escalation attacks where attackers can bypass security controls that would normally prevent them from executing malicious scripts or binaries. In enterprise environments, this could enable attackers to establish backdoors, exfiltrate data, or deploy additional malware while remaining undetected by standard security monitoring systems. The impact extends beyond individual systems to potentially affect entire network infrastructures, particularly in environments where PowerShell is heavily used for administrative tasks and where Device Guard policies are expected to provide robust protection against code injection attacks.
Mitigation strategies for CVE-2018-8492 should focus on immediate patch application from Microsoft as the primary defense mechanism, alongside enhanced monitoring of PowerShell execution activities and code integrity policy violations. Organizations should implement comprehensive logging and alerting for PowerShell events, particularly those involving script execution and policy bypass attempts, aligning with the monitoring requirements outlined in the MITRE ATT&CK framework for PowerShell abuse techniques. Security teams should also consider implementing additional layers of protection such as AppLocker policies, PowerShell script block logging, and enhanced network monitoring to detect anomalous behavior that might indicate exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates the critical nature of code integrity enforcement mechanisms in enterprise security architectures, with implications for compliance requirements under standards such as NIST SP 800-53 and ISO 27001 that mandate proper access control and code integrity measures. Organizations should also review their existing Device Guard policies to ensure they are properly configured and that any bypass attempts are detected and investigated promptly.