CVE-2017-9138 in FH1202
Summary
by MITRE
There is a debug-interface vulnerability on some Tenda routers (FH1202/F1202/F1200: versions before 1.2.0.20). After connecting locally to a router in a wired or wireless manner, one can bypass intended access restrictions by sending shell commands directly and reading their results, or by entering shell commands that change this router's username and password.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/01/2020
The vulnerability identified as CVE-2017-9138 represents a critical security flaw in certain Tenda router models including FH1202 F1202 and F1200 devices. This issue stems from an improperly secured debug interface that exists within the router firmware, specifically affecting versions prior to 1.2.0.20. The vulnerability allows unauthorized local access to the router's command execution environment through a direct connection either via wired or wireless means, fundamentally undermining the device's security posture.
The technical exploitation of this vulnerability occurs through a debug interface that should be restricted to authorized administrators only but remains accessible to any local user who can establish a connection to the router. This flaw enables attackers to execute arbitrary shell commands directly on the affected devices, providing them with complete control over the router's operational functions. The vulnerability specifically affects the authentication mechanisms within the router's firmware, allowing malicious actors to bypass normal access controls and gain root-level privileges without proper authorization.
From an operational impact perspective, this vulnerability creates a significant risk for network security as it allows attackers to completely compromise the affected routers. Once exploited, adversaries can modify router configurations, change administrative credentials, redirect network traffic, or even install malicious firmware. The local access requirement means that physical proximity to the device is necessary for exploitation, but this limitation does not prevent determined attackers from gaining access through social engineering, insider threats, or by simply connecting to public networks where these routers might be deployed.
The vulnerability aligns with CWE-284, which addresses improper access control issues, and demonstrates a clear failure in implementing proper authentication and authorization mechanisms within the router's firmware. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1059.004 for command and scripting interpreter and T1566 for credential access through network infrastructure devices. The security implications extend beyond simple privilege escalation as the compromised router can serve as a pivot point for lateral movement within the network, potentially enabling more sophisticated attacks.
Mitigation strategies for this vulnerability primarily involve updating the affected router firmware to version 1.2.0.20 or later, which contains the necessary security patches to close the debug interface access. Network administrators should also implement network segmentation to isolate critical infrastructure devices and consider disabling unused services on routers. Additionally, regular security audits of network devices and implementing robust access control policies can help prevent exploitation of similar vulnerabilities in other network equipment. The incident highlights the importance of secure firmware development practices and proper security testing of network devices before deployment.