CVE-2020-14075 in TEW-827DRU
Summary
by MITRE
TRENDnet TEW-827DRU devices through 2.06B04 contain multiple command injections in apply.cgi via the action pppoe_connect, ru_pppoe_connect, or dhcp_connect with the key wan_ifname (or wan0_dns), allowing an authenticated user to run arbitrary commands on the device.
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Analysis
by VulDB Data Team • 06/15/2020
The CVE-2020-14075 vulnerability affects TRENDnet TEW-827DRU wireless routers running firmware versions up to 2.06B04, representing a critical command injection flaw that exploits the apply.cgi web interface. This vulnerability stems from inadequate input validation and sanitization within the router's web management interface, specifically targeting the pppoe_connect, ru_pppoe_connect, and dhcp_connect actions. The flaw manifests when an authenticated user manipulates the wan_ifname or wan0_dns parameters, which are processed without proper sanitization, creating an avenue for arbitrary code execution on the underlying device. The vulnerability resides in the router's handling of user-supplied parameters within the web application's backend processing logic, where input values are directly incorporated into system commands without appropriate escaping or filtering mechanisms.
The technical exploitation of this vulnerability follows the patterns defined by CWE-77 and CWE-94, which classify it as a command injection vulnerability that allows attackers to execute arbitrary system commands through improperly validated user input. The attack vector requires an authenticated session, typically through legitimate administrative credentials, which aligns with ATT&CK technique T1078 for valid accounts and T1059 for command and scripting interpreter. When an attacker submits malicious input through the affected parameters, the router's web server processes these inputs directly within shell commands, bypassing normal security controls and allowing complete system compromise. The vulnerability affects the router's WAN configuration management functions, where the device's operating system executes commands based on user input from the web interface, creating a direct path to system-level execution.
The operational impact of CVE-2020-14075 extends beyond simple unauthorized command execution, as it provides attackers with complete control over the affected router's functionality. Once exploited, an attacker can modify network configurations, redirect traffic, establish backdoors, or use the device as a pivot point for further attacks within the local network. The vulnerability affects not only the router's immediate functionality but also compromises the security of all devices connected to the network, as the compromised router can serve as a gateway for lateral movement. The authenticated nature of the vulnerability means that attackers typically need to obtain valid administrative credentials through social engineering, credential reuse, or other initial compromise techniques before exploiting this command injection flaw. This makes the vulnerability particularly dangerous in environments where administrative credentials are weak or reused across multiple devices.
Mitigation strategies for CVE-2020-14075 should prioritize immediate firmware updates from TRENDnet to address the underlying command injection vulnerability. Organizations should implement network segmentation to limit the impact of potential exploitation and ensure that administrative credentials are strong and unique, following NIST SP 800-116 guidelines for credential management. Network monitoring should be enhanced to detect unusual traffic patterns or command execution attempts that might indicate exploitation attempts. Additionally, implementing web application firewalls and input validation controls can provide additional defense-in-depth layers. Security teams should also conduct regular vulnerability assessments and penetration testing to identify similar command injection vulnerabilities in other network devices, particularly those running embedded operating systems with web interfaces. The vulnerability highlights the importance of proper input validation and secure coding practices, particularly when handling user-supplied data in system command execution contexts, aligning with OWASP Top 10 security principles for preventing injection flaws.