CVE-2020-5894 in Controller
Summary
by MITRE
On versions 3.0.0-3.3.0, the NGINX Controller webserver does not invalidate the server-side session token after users log out.
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Analysis
by VulDB Data Team • 05/08/2020
The vulnerability identified as CVE-2020-5894 affects NGINX Controller versions 3.0.0 through 3.3.0, representing a critical session management flaw that undermines the security posture of the web-based administration interface. This issue resides within the authentication and session handling mechanisms of the NGINX Controller platform, which is designed to provide centralized management for NGINX Plus and NGINX Open Source deployments. The vulnerability specifically targets the server-side session token invalidation process, creating a persistent security weakness that can be exploited by unauthorized parties.
The technical flaw manifests when users log out of the NGINX Controller web interface, as the system fails to properly invalidate the server-side session token associated with that user session. This creates a session fixation vulnerability where an attacker who has obtained a valid session token can continue to use it even after the legitimate user has logged out. The root cause lies in improper session management implementation where the logout functionality does not properly terminate the server-side session state, leaving the session token in an active state that can be reused by any party possessing the token. This behavior violates fundamental security principles for session management and authentication handling.
The operational impact of this vulnerability is significant as it allows for unauthorized access to administrative functions and sensitive configuration data within the NGINX Controller environment. An attacker who gains access to a valid session token can maintain persistent access to the controller's web interface without requiring re-authentication, potentially enabling them to modify configurations, deploy new applications, or access confidential network management data. The vulnerability essentially creates a backdoor that bypasses normal authentication controls, allowing attackers to operate within the administrative environment with the privileges of the compromised user account. This poses particular risk in environments where the controller manages critical network infrastructure components.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to a patched version of NGINX Controller that properly invalidates session tokens upon logout. The vulnerability aligns with CWE-613, which addresses insufficient session expiration, and represents a clear violation of the principle of least privilege in authentication systems. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and privilege escalation, as attackers can leverage the persistent session to maintain administrative access. Additional mitigations should include implementing network segmentation, monitoring for unusual session activity, and ensuring that session tokens are properly invalidated through secure session management practices. The fix typically involves ensuring that the logout process properly destroys the server-side session state and invalidates any associated tokens, preventing session reuse attacks.