CVE-2017-16106 in tmock
Summary
by MITRE
tmock is a static file server. tmock is vulnerable to a directory traversal issue, giving an attacker access to the filesystem by placing "../" in the url.
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Analysis
by VulDB Data Team • 02/15/2020
The vulnerability identified as CVE-2017-16106 affects tmock, a static file server implementation that serves web content from local directories. This particular flaw represents a classic directory traversal vulnerability that allows unauthorized access to the underlying filesystem through improper input validation. The vulnerability exists when the application fails to properly sanitize user-supplied input that is used to construct file paths, enabling attackers to navigate beyond the intended directory boundaries. The specific mechanism involves the manipulation of URL paths using the "../" sequence, which when processed by the server, can cause the application to access files outside of its designated serving directory. This type of vulnerability is particularly dangerous as it can potentially expose sensitive system files, configuration data, or other confidential information stored on the server.
The technical exploitation of this vulnerability aligns with CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. This flaw falls under the broader category of insecure direct object references and represents a fundamental failure in input validation and access control mechanisms. Attackers can leverage this vulnerability by crafting malicious URLs that include directory traversal sequences, effectively bypassing the intended file serving restrictions. The impact extends beyond simple information disclosure as it may enable attackers to access system files, execute arbitrary code, or potentially escalate privileges depending on the server's configuration and the permissions of the running process. The vulnerability is particularly concerning in environments where the static file server is not properly isolated from sensitive system resources.
The operational impact of this vulnerability can be severe for organizations relying on tmock for serving static content. An attacker with access to the vulnerable service can potentially discover and retrieve any file accessible to the server process, including sensitive configuration files, database credentials, application source code, or system logs. This exposure can lead to complete system compromise, especially if the server process runs with elevated privileges or has access to databases or other critical system resources. The vulnerability also enables potential denial of service conditions if attackers can access and manipulate critical system files or directories, causing the server to malfunction or become unavailable. Additionally, the exposure of source code or configuration files can provide attackers with additional attack vectors and information about the system architecture. From an adversarial perspective, this vulnerability maps to several ATT&CK techniques including TA0007 Discovery for information gathering and TA0006 Credential Access for potential credential exposure, making it a valuable target for threat actors.
Mitigation strategies for CVE-2017-16106 should focus on implementing proper input validation and sanitization mechanisms to prevent directory traversal attempts. Organizations should ensure that all user-supplied input is rigorously validated before being used in file path construction, implementing strict whitelisting of allowed characters and path components. The application should normalize all file paths and reject any requests containing traversal sequences such as "../" or "..\". Additionally, the server should operate with minimal required privileges and be properly isolated from sensitive system resources. Regular security updates and patches should be applied to tmock and any related dependencies. Implementing web application firewalls or security controls that can detect and block directory traversal patterns in incoming requests provides an additional layer of defense. Organizations should also conduct regular security testing including penetration testing and code reviews to identify and remediate similar vulnerabilities in other applications and systems. The implementation of proper access controls and the principle of least privilege should be enforced to minimize the potential impact of any successful exploitation attempts.