CVE-2019-10157 in KeyCloak
Summary
by MITRE
It was found that Keycloak's Node.js adapter before version 4.8.3 did not properly verify the web token received from the server in its backchannel logout . An attacker with local access could use this to construct a malicious web token setting an NBF parameter that could prevent user access indefinitely.
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Analysis
by VulDB Data Team • 10/05/2023
The vulnerability described in CVE-2019-10157 affects Keycloak's Node.js adapter version 4.8.2 and earlier, representing a critical security flaw in the authentication and session management system. This issue specifically targets the backchannel logout functionality, which is a crucial component of single sign-out mechanisms in identity management systems. The vulnerability stems from improper validation of JSON Web Tokens (JWT) received during the logout process, creating a significant risk for organizations relying on Keycloak for authentication services. The flaw allows attackers to manipulate token parameters in a way that could permanently block user access to applications protected by Keycloak.
The technical root cause of this vulnerability lies in the inadequate validation of the Not Before (NBF) claim within JWT tokens used for backchannel logout operations. The NBF parameter is a standard JWT claim that specifies the time before which the token must not be accepted for processing. In the affected Keycloak versions, the Node.js adapter failed to properly validate this parameter, allowing malicious actors to craft tokens with future-dated NBF values. This manipulation effectively creates a time-based access control bypass where users become permanently locked out of their sessions until the future timestamp passes, rendering the authentication system ineffective for those specific users. The vulnerability operates at the application layer and requires local access to exploit, making it particularly dangerous as it can be leveraged by attackers with limited system privileges.
The operational impact of this vulnerability extends beyond simple access denial, as it represents a complete breakdown in session management and user access control. Organizations using Keycloak for authentication could experience extended periods of user lockout, potentially affecting business operations and user productivity. The indefinite nature of the access restriction means that users might remain locked out for hours or days until the manipulated NBF timestamp expires naturally. This vulnerability directly violates security principles of availability and access control, as legitimate users cannot access their accounts while the malicious token remains in the system. The issue also demonstrates poor input validation practices that could potentially be exploited in combination with other vulnerabilities to create more severe attack scenarios.
Organizations should immediately upgrade their Keycloak Node.js adapter to version 4.8.3 or later to remediate this vulnerability, as this represents the official fix provided by the Keycloak development team. The mitigation strategy involves not only updating the software but also implementing additional monitoring for suspicious logout activities and token validation failures. Security teams should conduct thorough assessments of their Keycloak deployments to identify any instances where the vulnerable adapter is in use, particularly in environments where local access might be compromised. The vulnerability aligns with CWE-290 validation of certificate with incorrect trust anchor, as it involves improper validation of security tokens that should be trusted. This issue also maps to ATT&CK technique T1566.002 social engineering phishing, as attackers could potentially exploit this vulnerability to maintain persistent access to user accounts through manipulated token parameters. Regular security audits of authentication systems and implementation of proper token validation mechanisms should be prioritized to prevent similar vulnerabilities in the future, emphasizing the importance of robust input validation and proper security controls in identity management systems.