CVE-2019-1006 in .NET Framework
Summary
by MITRE
An authentication bypass vulnerability exists in Windows Communication Foundation (WCF) and Windows Identity Foundation (WIF), allowing signing of SAML tokens with arbitrary symmetric keys, aka 'WCF/WIF SAML Token Authentication Bypass Vulnerability'.
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Analysis
by VulDB Data Team • 07/09/2020
The vulnerability identified as CVE-2019-1006 represents a critical authentication bypass flaw affecting Windows Communication Foundation and Windows Identity Foundation components within Microsoft's ecosystem. This weakness enables attackers to manipulate SAML token signatures using arbitrary symmetric keys, fundamentally undermining the security assurances that these identity frameworks are designed to provide. The vulnerability stems from insufficient validation mechanisms within the token processing pipeline, creating an avenue for malicious actors to forge authentication tokens that would otherwise be rejected by legitimate systems.
Technical exploitation of this vulnerability occurs through the manipulation of SAML token signature validation processes within WCF and WIF implementations. The flaw allows attackers to bypass the normal cryptographic verification steps that should ensure token integrity and authenticity. When systems process SAML tokens, they typically verify the digital signature using predefined keys or certificate chains to confirm the token's origin and integrity. However, this vulnerability permits attackers to substitute their own symmetric keys during the signature verification process, effectively allowing them to create valid-looking tokens that can authenticate as any user or system within the targeted environment.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with the capability to impersonate legitimate users and systems across federated identity environments. Organizations relying on WCF and WIF for secure communication and identity management face significant risk when this vulnerability exists, as it can lead to complete compromise of authentication mechanisms. The vulnerability affects systems that utilize SAML-based authentication, particularly those implementing federated identity solutions where trust relationships between different security domains are established through token exchange processes. Attackers can leverage this weakness to escalate privileges, access restricted resources, and potentially move laterally within networks where these technologies are deployed.
Mitigation strategies for CVE-2019-1006 should prioritize immediate patch application from Microsoft, as the vulnerability has been addressed through security updates specifically targeting the flawed token validation logic. Organizations must ensure comprehensive testing of patched environments to verify that the fix properly resolves the signature validation bypass without introducing regressions in legitimate authentication workflows. Additional defensive measures include implementing network segmentation to limit exposure of vulnerable systems, monitoring authentication logs for suspicious token usage patterns, and reviewing existing security configurations to ensure that appropriate key management practices are in place. The vulnerability aligns with CWE-295 which addresses improper certificate validation, and relates to ATT&CK technique T1550.001 for use of valid accounts, as successful exploitation allows attackers to assume legitimate user identities within the affected systems. Organizations should also consider implementing additional authentication controls such as multi-factor authentication to provide defense in depth against potential exploitation of this and similar vulnerabilities.