CVE-2017-17758 in TL-WVR
Summary
by MITRE
TP-Link TL-WVR and TL-WAR devices allow remote authenticated users to execute arbitrary commands via shell metacharacters in the interface field of an admin/dhcps command to cgi-bin/luci, related to the zone_get_iface_bydev function in /usr/lib/lua/luci/controller/admin/dhcps.lua in uhttpd.
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Analysis
by VulDB Data Team • 01/27/2021
This vulnerability exists in TP-Link TL-WVR and TL-WAR wireless router devices running uhttpd web server software. The flaw resides in the administrative web interface where the zone_get_iface_bydev function in the /usr/lib/lua/luci/controller/admin/dhcps.lua file fails to properly sanitize user input. When authenticated administrators access the cgi-bin/luci endpoint with a maliciously crafted interface field parameter containing shell metacharacters, the system executes arbitrary commands with the privileges of the web server process. This represents a classic command injection vulnerability that allows remote authenticated attackers to gain unauthorized control over the affected devices. The vulnerability stems from insufficient input validation and improper shell command construction within the LuCI web framework implementation. According to CWE-77, this falls under improper neutralization of special elements used in a command, specifically manifesting as command injection through web interface parameters. The attack requires an authenticated user with administrative privileges, making it a privilege escalation vulnerability rather than a purely remote exploit. However, the impact remains significant as it allows attackers who have already gained administrative access to escalate their privileges further or execute arbitrary code on the device.
The operational impact of this vulnerability extends beyond simple command execution, as it enables attackers to modify network configurations, access sensitive device information, and potentially use the compromised device as a pivot point for attacking other systems within the network. The affected devices typically run embedded Linux systems where the web server process operates with elevated privileges, making successful exploitation particularly dangerous. Attackers can leverage this vulnerability to install backdoors, modify firewall rules, redirect traffic, or even compromise the entire network infrastructure. The vulnerability affects multiple TP-Link models including the TL-WVR series and TL-WAR series, which are commonly deployed in both residential and small business environments. These devices often serve as the primary gateway for network traffic, making them attractive targets for attackers seeking persistent access to larger networks. The issue is particularly concerning because it allows attackers to execute commands with the same privileges as the web server process, which typically has access to system resources and network interfaces. According to ATT&CK framework, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: Shell Script) and T1068 (Exploitation for Privilege Escalation) techniques. The vulnerability demonstrates poor input validation practices and highlights the importance of secure coding principles in embedded web applications.
Mitigation strategies for this vulnerability should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves applying firmware updates from TP-Link that contain proper input sanitization and validation for the affected functions. Network administrators should ensure that all affected devices are updated to the latest firmware versions available from the manufacturer. Additionally, implementing network segmentation and access controls can limit the potential impact of successful exploitation. The vulnerability can be mitigated through proper input validation techniques such as parameterized queries and strict input sanitization, which would prevent shell metacharacters from being interpreted as commands. Organizations should also consider implementing web application firewalls to detect and block suspicious requests to the cgi-bin/luci endpoint. Regular security audits of embedded web applications should be conducted to identify similar vulnerabilities in other network devices. The root cause of this vulnerability emphasizes the need for secure coding practices in embedded systems, particularly when handling user input in web interfaces. Implementing proper input validation, using secure coding standards, and conducting regular penetration testing can prevent similar issues from occurring in other network infrastructure components. Given the nature of the vulnerability, it is recommended that organizations review their entire network device inventory for similar command injection vulnerabilities and ensure that all administrative interfaces properly validate and sanitize user input before processing.