CVE-2021-31590 in PwnDoc
Summary
by MITRE • 07/20/2021
PwnDoc through 2021-04-22 has incorrect JSON Webtoken handling, leading to incorrect access control. With a valid JSON Webtoken that is used for authentication and authorization, a user can keep his admin privileges even if he is downgraded to the "user" privilege. Even after a user's account is deleted, the user can still access the administration panel (and add or delete users) and has complete access to the system.
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Analysis
by VulDB Data Team • 07/22/2021
The vulnerability identified as CVE-2021-31590 affects PwnDoc version 2021-04-22 and earlier, representing a critical flaw in the application's authentication and authorization mechanisms. This issue stems from improper handling of JSON Web Tokens which are fundamental to modern web application security architectures. The vulnerability manifests when a user possesses a valid JSON Web Token that should be revoked upon privilege changes or account deletion, yet continues to maintain administrative access. This represents a severe breakdown in the principle of least privilege and role-based access control that forms the foundation of secure application design. The flaw allows attackers to maintain elevated privileges even after legitimate administrative actions should have revoked their access rights.
The technical implementation of this vulnerability involves the application's failure to properly validate or invalidate JSON Web Tokens when user privileges are modified or accounts are removed. When a user's role is downgraded from administrator to regular user, the system should invalidate the existing token and require re-authentication with appropriate credentials. Similarly, when an account is deleted, the corresponding token should be immediately invalidated to prevent continued access. However, PwnDoc's implementation fails to perform these critical token validation steps, creating a persistent access control flaw that can be exploited by malicious actors. This vulnerability directly relates to CWE-285 which addresses improper authorization in authentication mechanisms, and CWE-345 which covers insufficient verification of data integrity. The flaw operates at the application layer and can be classified under the ATT&CK technique T1078 which involves valid accounts and credential access.
The operational impact of this vulnerability is severe and far-reaching for any organization using PwnDoc. An attacker who gains access to a valid JSON Web Token can maintain administrative privileges indefinitely, allowing them to perform unauthorized actions such as adding new users, deleting existing users, modifying system configurations, and accessing sensitive data. This persistent access bypasses all normal security controls and can lead to complete system compromise. The vulnerability is particularly dangerous because it persists even after account deletion, meaning that simply removing a user from the system does not prevent continued access. The implications extend beyond simple privilege escalation to include potential data exfiltration, system manipulation, and complete loss of administrative control. Organizations may face regulatory compliance violations and significant operational disruption when such vulnerabilities are exploited in production environments.
Mitigation strategies for CVE-2021-31590 must address the core token management issues within PwnDoc. The primary recommendation involves implementing proper token invalidation mechanisms that automatically revoke JSON Web Tokens when user privileges change or accounts are deleted. This requires the application to maintain an active token revocation list or implement short-lived tokens with proper refresh mechanisms. Organizations should also implement token binding techniques that tie tokens to specific sessions and user contexts, preventing reuse across different privilege levels. Additionally, the system should enforce immediate token invalidation upon account modification or deletion events. Security updates and patches should be applied immediately to address this vulnerability, as the flaw allows persistent access that can be exploited for extended periods. Regular security audits of authentication systems should include verification of token handling procedures to prevent similar issues from arising in the future. The implementation of these mitigations aligns with security best practices outlined in NIST SP 800-63B for digital identity management and the OWASP authentication cheat sheet recommendations for secure token handling.