CVE-2019-16929 in Auth0
Summary
by MITRE
Auth0 auth0.net before 6.5.4 has Incorrect Access Control because IdentityTokenValidator can be accidentally used to validate untrusted ID tokens.
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Analysis
by VulDB Data Team • 09/28/2020
The vulnerability identified as CVE-2019-16929 affects Auth0 auth0.net versions prior to 6.5.4 and represents a critical access control flaw that undermines the security of authentication systems relying on this component. This issue stems from the IdentityTokenValidator class which is designed to validate identity tokens but can be inadvertently configured or used in ways that permit validation of untrusted ID tokens. The flaw creates a scenario where malicious actors could potentially exploit this misconfiguration to bypass authentication mechanisms and gain unauthorized access to protected resources. The vulnerability specifically targets the validation process of identity tokens, which are critical components in modern authentication architectures that establish user identity and permissions within applications and services.
The technical root cause of this vulnerability lies in improper validation controls within the IdentityTokenValidator implementation, which fails to adequately verify the trustworthiness of identity tokens before accepting them as valid. This flaw allows for what is classified as incorrect access control under the Common Weakness Enumeration framework as CWE-284, where the system grants inappropriate access permissions due to insufficient validation of authentication tokens. The vulnerability occurs when the IdentityTokenValidator is configured to accept tokens from untrusted sources without proper verification mechanisms, creating a pathway for attackers to submit forged or manipulated identity tokens that the system accepts as legitimate. This misconfiguration essentially disables the intended security checks that should prevent unauthorized access, thereby undermining the entire authentication flow.
The operational impact of this vulnerability extends beyond simple authentication bypasses and can lead to severe consequences including unauthorized data access, privilege escalation, and potential system compromise. Attackers exploiting this vulnerability could gain access to sensitive user information, perform actions with elevated privileges, and potentially establish persistent access within affected systems. The vulnerability affects any application or service that relies on Auth0 for authentication and uses the IdentityTokenValidator component in a manner that allows untrusted token validation. Organizations implementing this authentication system may experience unauthorized access to protected resources, data breaches, and violations of security policies that govern access control and authentication mechanisms.
Mitigation strategies for this vulnerability require immediate patching of the affected Auth0 auth0.net component to version 6.5.4 or later, which contains the necessary fixes to properly validate identity tokens and prevent the acceptance of untrusted tokens. Security teams should also conduct thorough audits of their authentication configurations to ensure that IdentityTokenValidator is properly configured to only validate tokens from trusted sources and that appropriate validation mechanisms are in place. Additional defensive measures include implementing proper token validation policies, monitoring authentication logs for suspicious activities, and ensuring that all identity tokens undergo rigorous verification before being accepted as valid. Organizations should also consider implementing additional layers of security such as multi-factor authentication and continuous monitoring to reduce the impact of potential exploitation attempts. The vulnerability highlights the importance of proper access control implementation and validation of authentication tokens, aligning with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting, which are common attack patterns that leverage authentication system weaknesses.