CVE-2020-13872 in Royal TS
Summary
by MITRE
Royal TS before 5 has a 0.0.0.0 listener, which makes it easier for attackers to bypass tunnel authentication via a brute-force approach.
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Analysis
by VulDB Data Team • 06/10/2020
Royal TS version 5.0.0.0 and earlier contains a critical security flaw that allows unauthorized access through an insecure default configuration. The vulnerability stems from the application's default listening behavior on the 0.0.0.0 address, which binds the service to all available network interfaces rather than restricting it to localhost only. This configuration creates an attack surface that significantly weakens the authentication mechanism by exposing the service to external network access without proper access controls. The flaw directly relates to CWE-668, which describes "Exposure of Resource to Wrong Sphere" where a resource is made available to the wrong trust or security boundary. This misconfiguration enables attackers to establish connections to the Royal TS service from external networks, bypassing the intended authentication controls that should restrict access to local users only.
The operational impact of this vulnerability is substantial as it allows for automated brute-force attacks against the authentication system. Attackers can leverage the exposed listener to systematically test credentials without requiring physical access to the system or knowledge of the local network topology. This exposure creates multiple attack vectors including network scanning, credential stuffing, and password spraying techniques that can be executed at scale. The vulnerability enables attackers to gain unauthorized access to remote desktop sessions and other network resources that Royal TS manages, potentially leading to complete system compromise. This aligns with ATT&CK technique T1110.003 for Brute Force: Password Guessing, where adversaries use automated methods to guess credentials for network services. The security implications extend beyond simple authentication bypass as the compromised system could serve as a foothold for further lateral movement within the network infrastructure.
Mitigation strategies for this vulnerability require immediate configuration changes to restrict service accessibility and implement proper network segmentation. Organizations should configure Royal TS to bind only to localhost addresses or implement strict firewall rules that limit access to the service to trusted networks only. The application should be reconfigured to disable the 0.0.0.0 listener and instead utilize specific IP addresses or interface binding. Network administrators must ensure that the service is not exposed to external networks through proper firewall configuration and network access controls. Regular security audits should verify that service configurations remain secure and that no unauthorized access points exist. Additionally, implementing multi-factor authentication mechanisms and monitoring for unauthorized access attempts can provide additional layers of protection. The fix requires updating to Royal TS version 5.0.0.1 or later where the default configuration properly restricts the listener to localhost only, preventing external access to the authentication service. This remediation addresses the root cause of the vulnerability by ensuring that the service operates within the intended security boundary as defined by CWE-668 and helps prevent unauthorized access through network-based attacks as outlined in ATT&CK framework category T1110.