CVE-2017-0173 in Windows
Summary
by MITRE
Microsoft Windows 10 1607 and Windows Server 2016 allow an attacker to exploit a security feature bypass vulnerability in Device Guard that could allow the attacker to inject malicious code into a Windows PowerShell session, aka "Device Guard Code Integrity Policy Security Feature Bypass Vulnerability." This CVE ID is unique from CVE-2017-0215, CVE-2017-0216, CVE-2017-0218, and CVE-2017-0219.
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Analysis
by VulDB Data Team • 12/27/2020
The vulnerability described in CVE-2017-0173 represents a critical security feature bypass in Microsoft Windows 10 version 1607 and Windows Server 2016 environments. This flaw specifically targets Device Guard, a security feature designed to enforce code integrity policies and prevent unauthorized code execution. The vulnerability allows attackers to circumvent the intended protections that Device Guard provides, creating a pathway for malicious code injection into Windows PowerShell sessions. This represents a significant escalation in attack capabilities since Device Guard is specifically engineered to prevent such scenarios, making this bypass particularly concerning for enterprise security architectures.
The technical implementation of this vulnerability stems from a flaw in how Device Guard validates code integrity policies when executing PowerShell commands. Attackers can exploit this weakness to inject malicious scripts or binaries into existing PowerShell sessions without triggering the normal security checks that Device Guard should enforce. The vulnerability specifically affects systems where Device Guard is enabled and running in enforcement mode, creating a scenario where legitimate security controls become ineffective. This bypass occurs at the policy validation layer, where the system fails to properly verify that code execution complies with configured integrity policies, allowing malicious code to execute with the privileges of the current PowerShell session.
The operational impact of this vulnerability extends beyond simple code injection, as it undermines the fundamental security model that Device Guard is designed to enforce. Organizations relying on Device Guard for protecting against script-based attacks and unauthorized code execution face a significant risk, as attackers can now bypass these protections without requiring additional privileges or exploiting other system vulnerabilities. This vulnerability particularly affects enterprise environments where PowerShell is heavily used for administrative tasks, as it allows attackers to execute malicious commands within legitimate administrative sessions, potentially leading to complete system compromise. The attack vector requires minimal privileges and can be executed remotely, making it a high-value target for threat actors seeking persistent access to enterprise networks.
Mitigation strategies for CVE-2017-0173 should focus on immediate patch deployment from Microsoft, as the vulnerability was addressed through the July 2017 security updates. Organizations should also implement additional monitoring for suspicious PowerShell activities and ensure that Device Guard policies are properly configured and enforced. The vulnerability aligns with CWE-284 Access Control Issues, specifically related to insufficient access control validation during code execution, and can be mapped to ATT&CK technique T1059.001 Command and Scripting Interpreter for PowerShell. Network administrators should consider implementing additional security controls such as PowerShell logging, script block logging, and restricting PowerShell execution policies to minimize the impact of such bypasses. Organizations should also review their existing Device Guard configurations to ensure that policies are properly enforced and that the security controls are not being inadvertently bypassed through configuration errors or misconfigurations.