CVE-2018-0786 in .NET
Summary
by MITRE
Microsoft .NET Framework 1.1, 2.0, 3.0, 3.5, 3.5.1, 4, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, and 4.7 and .NET Core 1.0 and 2.0 allow a security feature bypass vulnerability due to the way certificates are validated, aka ".NET Security Feature Bypass Vulnerability".
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Analysis
by VulDB Data Team • 01/29/2021
The CVE-2018-0786 vulnerability represents a critical security feature bypass in Microsoft .NET Framework versions 1.1 through 4.7 and .NET Core 1.0 and 2.0, fundamentally undermining certificate validation mechanisms that are essential for secure communications. This vulnerability stems from improper certificate validation logic that allows attackers to bypass security checks during SSL/TLS certificate verification processes, potentially enabling man-in-the-middle attacks and unauthorized access to protected resources. The flaw specifically affects the way the framework handles certificate trust relationships and validation chains, creating a pathway for malicious actors to establish fraudulent connections while appearing legitimate to the system.
The technical implementation of this vulnerability resides in the certificate validation algorithms within the .NET Framework's security subsystem, which fails to properly enforce certificate chain validation rules and trust assertions. This weakness enables attackers to exploit the validation process by manipulating certificate parameters or bypassing trust store checks, ultimately allowing them to establish secure connections with fraudulent certificates that would normally be rejected. The vulnerability operates at the core of the framework's cryptographic validation layer, where certificate validation occurs during SSL/TLS handshakes and secure communication establishment, making it particularly dangerous in environments where certificate-based authentication is paramount.
From an operational perspective, this vulnerability creates significant risks for organizations relying on .NET applications for secure communications, particularly in financial services, healthcare, and government sectors where certificate validation is critical for maintaining data integrity and confidentiality. Attackers can leverage this vulnerability to perform certificate pinning bypasses, establish unauthorized secure connections, and potentially intercept or manipulate sensitive data flowing through .NET applications. The impact extends beyond individual applications to encompass entire infrastructure components that depend on .NET Framework security features, potentially affecting thousands of systems across enterprise environments.
Organizations must implement immediate mitigations including applying the relevant Microsoft security patches released in the July 2018 security updates, which address the certificate validation logic flaws and restore proper certificate chain validation. Additionally, administrators should consider implementing certificate monitoring solutions to detect anomalous certificate usage patterns and deploy network-based detection measures to identify potential exploitation attempts. The vulnerability aligns with CWE-295, which addresses improper certificate validation, and maps to ATT&CK technique T1059.001 for execution through .NET frameworks, highlighting the need for comprehensive security hardening across all affected system components. Organizations should also review their certificate management policies and implement additional validation controls to reduce the attack surface and prevent exploitation of this security feature bypass vulnerability.