CVE-2018-3949 in TL-R600VPN
Summary
by MITRE
An exploitable information disclosure vulnerability exists in the HTTP server functionality of the TP-Link TL-R600VPN. A specially crafted URL can cause a directory traversal, resulting in the disclosure of sensitive system files. An attacker can send either an unauthenticated or an authenticated web request to trigger this vulnerability.
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Analysis
by VulDB Data Team • 06/12/2023
The CVE-2018-3949 vulnerability represents a critical directory traversal flaw in the TP-Link TL-R600VPN device's HTTP server implementation. This vulnerability stems from inadequate input validation within the web server component that processes incoming HTTP requests. The flaw allows remote attackers to manipulate URL parameters in a way that bypasses normal file access controls and retrieves arbitrary files from the device's file system. The vulnerability specifically affects the device's web interface functionality where user-supplied path information is not properly sanitized before being processed by the underlying file system operations. This type of vulnerability is classified as CWE-22 - Improper Limitation of a Pathname to a Restricted Directory - which is a well-documented weakness in web application security. The attack vector is particularly concerning because it can be executed without authentication, making it accessible to any remote user who can reach the device's web interface.
The technical exploitation of this vulnerability occurs when a malicious user crafts a specially formatted URL that includes directory traversal sequences such as "../" or similar path manipulation techniques. When the vulnerable web server processes this request, it fails to properly validate the requested file path, allowing the attacker to navigate through the file system hierarchy and access sensitive configuration files, system logs, and potentially credential information. The TP-Link TL-R600VPN device exposes its web management interface on port 80, making it susceptible to this attack from external networks. The vulnerability is particularly dangerous because it can be leveraged to extract system configuration files that may contain administrative passwords, encryption keys, or other sensitive data that could be used for further exploitation. According to ATT&CK framework, this vulnerability maps to T1083 - File and Directory Discovery, as it enables attackers to enumerate and access files on the target system.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked system files could provide attackers with comprehensive insights into the device's configuration and internal structure. Attackers could potentially extract the device's configuration files to understand network settings, user accounts, and security policies. The vulnerability also creates opportunities for more sophisticated attacks such as credential harvesting, which could enable persistent access to the network. The fact that this vulnerability can be exploited both unauthenticated and authenticated makes it particularly dangerous as it allows attackers to gain information even before establishing a legitimate session. This type of vulnerability often serves as a stepping stone for attackers to escalate privileges or conduct further reconnaissance. The security implications are compounded by the fact that many network administrators may not regularly update their embedded devices, leaving them vulnerable to such known exploits for extended periods.
Mitigation strategies for CVE-2018-3949 should include immediate firmware updates from TP-Link to address the directory traversal vulnerability. Network segmentation and firewall rules should be implemented to restrict access to the device's web interface, limiting exposure to only trusted networks. Additionally, implementing web application firewalls or intrusion prevention systems can help detect and block malicious URL patterns. Organizations should conduct regular vulnerability assessments of their network infrastructure to identify similar vulnerabilities in other embedded devices. The principle of least privilege should be enforced by limiting web interface access to only authorized personnel and implementing strong authentication mechanisms. Regular security audits of network devices should include checks for known vulnerabilities in firmware versions, with particular attention to devices that are often overlooked in traditional security assessments. The vulnerability also underscores the importance of secure coding practices in embedded systems, particularly in the validation of user-supplied input within web server components.