CVE-2023-34243 in TGstation
Summary
by MITRE • 06/09/2023
TGstation is a toolset to manage production BYOND servers. In affected versions if a Windows user was registered in tgstation-server (TGS), an attacker could discover their username by brute-forcing the login endpoint with an invalid password. When a valid Windows logon was found, a distinct response would be generated. This issue has been addressed in version 5.12.5. Users are advised to upgrade. Users unable to upgrade may be mitigated by rate-limiting API calls with software that sits in front of TGS in the HTTP pipeline such as fail2ban.
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Analysis
by VulDB Data Team • 07/07/2023
The vulnerability identified as CVE-2023-34243 affects TGstation server software, a toolset designed for managing production BYOND servers. This issue represents a significant security flaw in the authentication mechanism that specifically impacts Windows user accounts registered within the tgstation-server environment. The vulnerability stems from an insecure implementation of the login endpoint that fails to provide consistent response times or error messages regardless of whether a valid or invalid username is submitted during the authentication process. This inconsistency in response handling creates a timing-based side-channel attack vector that can be exploited by malicious actors to enumerate valid Windows usernames through systematic brute-force attempts.
The technical flaw manifests when an attacker submits login requests with invalid passwords while systematically varying the username parameter. The system's response behavior differs significantly between valid and invalid Windows logon names, with valid accounts generating a distinct response pattern that can be detected and analyzed by automated tools. This timing discrepancy occurs because the authentication system performs different processing paths for valid versus invalid accounts, with valid accounts requiring additional verification steps that introduce measurable delays. The vulnerability directly maps to CWE-200, which addresses Information Exposure Through Timing Discrepancies, and represents a classic example of how improper error handling can create security weaknesses in authentication systems.
The operational impact of this vulnerability extends beyond simple credential enumeration, as it provides attackers with a foothold for further exploitation attempts within the tgstation-server environment. Once valid usernames are discovered, attackers can focus subsequent brute-force efforts on specific accounts, significantly reducing the time and computational resources required to compromise user credentials. This vulnerability particularly affects organizations that rely on Windows authentication within their BYOND server infrastructure, creating potential risks for unauthorized access to production environments. The issue also demonstrates poor adherence to security best practices in API design, where the system should maintain consistent response patterns regardless of authentication success or failure to prevent information leakage.
Mitigation strategies for this vulnerability involve both immediate remediation and operational security measures. The most effective solution is upgrading to version 5.12.5, which addresses the timing discrepancy in authentication responses by implementing consistent error handling across all account validation attempts. Organizations unable to perform immediate upgrades can implement rate-limiting measures at the HTTP pipeline level using tools such as fail2ban to prevent automated brute-force attacks from overwhelming the authentication endpoint. Additionally, network-level firewalls and intrusion detection systems can be configured to monitor and block suspicious login patterns that exceed predetermined thresholds. The implementation of proper authentication rate-limiting aligns with ATT&CK technique T1110.003, which covers Credential Stuffing, and demonstrates the importance of layered security approaches in protecting authentication systems from automated exploitation attempts. Organizations should also consider implementing multi-factor authentication mechanisms to provide additional protection layers beyond simple username-password combinations, thereby reducing the overall risk surface exposed by such timing-based vulnerabilities.