CVE-2020-16136 in tgstation-server
Summary
by MITRE
In tgstation-server 4.4.0 and 4.4.1, an authenticated user with permission to download logs can download any file on the server machine (accessible by the owner of the server process) via directory traversal ../ sequences in /Administration/Logs/ requests. The attacker is unable to enumerate files, however.
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Analysis
by VulDB Data Team • 08/01/2020
This vulnerability exists in tgstation-server versions 4.4.0 and 4.4.1 where an authenticated user with specific permissions can exploit a directory traversal flaw to access arbitrary files on the server filesystem. The vulnerability manifests through the /Administration/Logs/ endpoint where directory traversal sequences using ../ can be injected into requests. This allows an attacker to navigate beyond the intended log directory and access files that should normally be restricted. The flaw represents a classic path traversal vulnerability that falls under CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory. The security impact is significant because it enables unauthorized file access to files that are accessible by the server process owner, potentially exposing sensitive configuration files, database credentials, or other system information.
The technical implementation of this vulnerability relies on the server's inadequate input validation and sanitization of user-supplied paths in the logs download functionality. When users request log files through the administration interface, the server processes the requested file path without proper validation to ensure it remains within the designated logs directory. This allows an attacker to manipulate the request by adding directory traversal sequences that move up the directory tree and access files outside of the intended scope. The vulnerability requires authentication and specific permissions to access the logs download functionality, but once exploited, it provides access to any file that the server process can read, regardless of the file's location in the filesystem. This attack vector aligns with ATT&CK technique T1083, which covers the discovery of files and directories, though the enumeration capability is limited as noted in the CVE description.
The operational impact of this vulnerability extends beyond simple file access as it can potentially expose sensitive system information that could be leveraged for further attacks. An attacker could potentially access configuration files that contain database connection strings, API keys, or other credentials that would allow for privilege escalation or lateral movement within the network. The vulnerability also poses a risk to data integrity and confidentiality, as it could expose system logs that might contain sensitive information about system operations or user activities. Organizations running tgstation-server versions 4.4.0 or 4.4.1 should be particularly concerned as this vulnerability could provide attackers with access to system resources that are typically protected from unauthorized access. The restricted enumeration capability means that while attackers cannot easily browse the filesystem, they can still target specific files once they know their locations, making this a particularly dangerous vulnerability for systems with sensitive data.
The recommended mitigation strategy involves immediate patching of the tgstation-server to version 4.4.2 or later where this vulnerability has been addressed. The fix should implement proper input validation and path sanitization to ensure that user-supplied paths cannot traverse beyond the intended directories. Organizations should also consider implementing additional access controls and monitoring for unusual file access patterns, particularly around the administration interfaces. The vulnerability highlights the importance of validating all user inputs and implementing the principle of least privilege, ensuring that even authenticated users cannot access resources beyond their intended scope. Security teams should also review their server configurations and implement proper logging and monitoring to detect potential exploitation attempts. This vulnerability serves as a reminder of the critical need for input validation and proper access controls in web applications, particularly those handling sensitive administrative functions.