CVE-2018-1039 in .NET Framework
Summary
by MITRE
A security feature bypass vulnerability exists in .Net Framework which could allow an attacker to bypass Device Guard, aka ".NET Framework Device Guard Security Feature Bypass Vulnerability." This affects Microsoft .NET Framework 4.7.1, Microsoft .NET Framework 4.6, Microsoft .NET Framework 3.5, Microsoft .NET Framework 4.7/4.7.1, Microsoft .NET Framework 3.0, Microsoft .NET Framework 3.5.1, Microsoft .NET Framework 4.5.2, Microsoft .NET Framework 4.6.2/4.7/4.7.1, Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1, Microsoft .NET Framework 2.0, Microsoft .NET Framework 4.6/4.6.1/4.6.2.
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Analysis
by VulDB Data Team • 03/11/2023
The CVE-2018-1039 vulnerability represents a critical security feature bypass in Microsoft's .NET Framework ecosystem that undermines the integrity of Device Guard enforcement mechanisms. This flaw specifically targets the Windows Defender Application Control (WDAC) policies that rely on .NET Framework components to validate code integrity and execution permissions. The vulnerability exists at the core of how .NET Framework handles code execution policies and certificate validation, creating an avenue for malicious actors to circumvent security controls that should prevent unauthorized code execution. Device Guard, as defined in the Microsoft Security Response Center documentation, is designed to enforce strict application whitelisting policies that prevent unsigned or untrusted executables from running on Windows systems, making this bypass particularly concerning for enterprise environments.
The technical implementation of this vulnerability stems from improper handling of code integrity checks within the .NET Framework's security subsystem, specifically in how it processes and validates digital signatures during runtime execution. The flaw manifests when .NET Framework components fail to properly enforce the Device Guard policies that are intended to restrict code execution based on certificate trust relationships and policy enforcement points. This issue is classified under CWE-284 Access Control Bypass, which indicates that the vulnerability allows unauthorized access to restricted resources by bypassing security mechanisms that should normally prevent such access. The vulnerability affects multiple versions of the .NET Framework across different release lines, indicating a fundamental flaw in the security model implementation rather than a simple patchable error. Attackers can exploit this weakness by crafting malicious code that leverages the flawed certificate validation routines to execute unauthorized payloads while appearing to comply with Device Guard policies.
The operational impact of this vulnerability extends beyond simple privilege escalation scenarios to encompass complete bypass of application control mechanisms that organizations rely upon for endpoint security. Security teams implementing Device Guard policies may find their protective measures rendered ineffective, as attackers can execute malicious code without proper certificate validation or policy enforcement. This vulnerability directly impacts the integrity of Windows security controls and can lead to persistent threats within enterprise environments where Device Guard is deployed as a primary defense mechanism. Organizations using .NET Framework applications in environments with strict security policies face increased risk of lateral movement and privilege escalation attacks, as the vulnerability allows bypass of the very controls designed to prevent such scenarios. The broad scope of affected .NET Framework versions means that organizations must conduct comprehensive inventory assessments to identify all potentially vulnerable systems.
Mitigation strategies for CVE-2018-1039 require immediate deployment of Microsoft security updates that address the specific code integrity validation flaws within affected .NET Framework versions. Organizations should prioritize patching all affected systems, particularly those running Device Guard policies, as the vulnerability can be exploited without user interaction and requires minimal attack surface. System administrators should also consider implementing additional monitoring controls to detect suspicious code execution patterns that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1134 Privilege Escalation and T1059 Command and Scripting Interpreter, as attackers can leverage the bypass to execute arbitrary code with elevated privileges. Network segmentation and application whitelisting should be reinforced as additional defensive measures, while security information and event management systems should be configured to alert on anomalous .NET Framework behavior that might indicate exploitation attempts. Organizations should also review their Device Guard policies to ensure proper enforcement of code integrity controls and consider implementing additional verification mechanisms beyond the standard .NET Framework validation processes.