CVE-2017-16897 in passport-wsfed-saml2
Summary
by MITRE
A vulnerability has been discovered in the Auth0 passport-wsfed-saml2 library affecting versions < 3.0.5. This vulnerability allows an attacker to impersonate another user and potentially elevate their privileges if the SAML identity provider does not sign the full SAML response (e.g., only signs the assertion within the response).
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Analysis
by VulDB Data Team • 12/18/2019
The vulnerability identified as CVE-2017-16897 resides within the Auth0 passport-wsfed-saml2 library, a critical component used for implementing SAML-based authentication in web applications. This flaw affects versions prior to 3.0.5 and represents a significant security weakness that directly impacts the integrity of user authentication processes. The vulnerability specifically targets the SAML response validation mechanism, creating a potential pathway for unauthorized privilege escalation and user impersonation attacks. The issue arises from inadequate validation of SAML responses when the identity provider fails to sign the complete SAML response, leaving the authentication system vulnerable to manipulation.
The technical flaw manifests when the SAML identity provider only signs the assertion portion of the SAML response rather than the entire response structure. This partial signing creates a validation gap that attackers can exploit by crafting malicious SAML responses that appear legitimate to the relying party. The vulnerability stems from the library's insufficient verification of the SAML response integrity, allowing an attacker to modify the assertion content while maintaining the appearance of a valid authentication flow. This behavior directly violates security principle of input validation and response integrity checking, as outlined in CWE-295 for certificate validation failures and CWE-347 for insufficient verification of cryptographic signatures. The flaw essentially allows attackers to manipulate the subject identifier and other critical attributes within the SAML assertion, enabling them to assume the identity of other users within the system.
The operational impact of this vulnerability extends beyond simple user impersonation to potentially enable privilege escalation within affected systems. When an application relies on the passport-wsfed-saml2 library for authentication, an attacker who successfully exploits this vulnerability can gain unauthorized access to resources and data that belong to other users. This creates a significant risk for enterprise applications that depend on SAML authentication, particularly those handling sensitive data or administrative functions. The attack vector becomes particularly dangerous in environments where the SAML identity provider is configured to sign only assertions rather than complete responses, which is a common configuration in many enterprise deployments. The vulnerability also aligns with ATT&CK technique T1566 for credential access through social engineering and T1078 for valid accounts usage, as it enables attackers to leverage legitimate authentication flows to gain unauthorized access.
Mitigation strategies for CVE-2017-16897 primarily focus on upgrading the affected library to version 3.0.5 or later, which includes proper validation of SAML response signatures. Organizations should also implement additional security controls such as enforcing complete SAML response signing by identity providers, implementing proper monitoring for suspicious authentication patterns, and conducting regular security assessments of authentication flows. The fix addresses the core validation issue by ensuring that the library verifies the integrity of the entire SAML response rather than relying solely on assertion-level signatures. Security teams should also consider implementing additional layers of authentication verification, such as multi-factor authentication, to reduce the impact of potential exploitation attempts. The vulnerability highlights the importance of proper cryptographic validation in authentication libraries and underscores the need for comprehensive security testing of identity management components. Organizations must also review their SAML configuration practices to ensure that identity providers are properly configured to sign complete responses rather than partial content, as this represents a fundamental security control that directly impacts the vulnerability's exploitability.