CVE-2016-0132 in Windows
Summary
by MITRE
Microsoft .NET Framework 2.0 SP2, 3.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, and 4.6.1 mishandles signature validation for unspecified elements of XML documents, which allows remote attackers to spoof signatures via a modified document, aka ".NET XML Validation Security Feature Bypass."
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-0132 represents a critical security flaw in Microsoft .NET Framework versions 2.0 SP2, 3.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, and 4.6.1 that fundamentally undermines the integrity of XML signature validation mechanisms. This weakness specifically affects how the framework processes signature validation for unspecified elements within XML documents, creating a security bypass that enables malicious actors to forge digital signatures without detection. The flaw resides in the XML validation security features that are designed to ensure document authenticity and integrity, yet fails to properly validate certain elements that are not explicitly defined in the XML schema or signature structure.
The technical implementation of this vulnerability stems from inadequate validation of XML signature elements, particularly when dealing with unspecified or optional components within XML documents. When the .NET Framework processes XML signatures, it should rigorously verify that all signature elements remain intact and unmodified during document processing. However, the vulnerability allows attackers to manipulate XML documents by modifying unspecified elements while maintaining the appearance of valid signatures, effectively bypassing the security checks that should prevent such modifications. This occurs because the framework's signature validation logic does not adequately account for all possible variations in XML structure that might occur in real-world applications, particularly when dealing with documents that contain optional or unspecified elements.
The operational impact of this vulnerability extends far beyond simple document integrity concerns, as it creates a significant attack surface for remote adversaries who can exploit this weakness to perform various malicious activities. Attackers can leverage this bypass to spoof digital signatures on XML documents, potentially gaining unauthorized access to systems that rely on XML signatures for authentication or authorization purposes. The vulnerability particularly affects applications that process XML documents from untrusted sources, including web services, email systems, and document management platforms that depend on .NET Framework's XML validation capabilities. This security bypass can lead to unauthorized data manipulation, privilege escalation, and potential system compromise when applications fail to detect that XML documents have been tampered with through signature spoofing.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security updates and patches released in response to this issue, which address the specific XML validation flaws in the affected .NET Framework versions. System administrators should also consider implementing additional security controls such as XML schema validation, input sanitization, and monitoring for suspicious XML document modifications. The vulnerability maps to CWE-295 which describes "Improper Certificate Validation" and relates to the broader category of security feature bypasses that can undermine cryptographic protections. From an ATT&CK perspective, this vulnerability aligns with techniques involving signature spoofing and credential access, potentially enabling adversaries to move laterally within networks or escalate privileges through manipulated XML-based authentication systems. Additionally, organizations should review their XML processing workflows and implement comprehensive logging to detect potential exploitation attempts, as the bypass may not always be immediately apparent to system administrators or security monitoring tools.