CVE-2017-16936 in Tenda Ac9
Summary
by MITRE
Directory Traversal vulnerability in app_data_center on Shenzhen Tenda Ac9 US_AC9V1.0BR_V15.03.05.14_multi_TD01, Ac9 ac9_kf_V15.03.05.19(6318_)_cn, Ac15 US_AC15V1.0BR_V15.03.05.18_multi_TD01, Ac15 US_AC15V1.0BR_V15.03.05.19_multi_TD01, Ac18 US_AC18V1.0BR_V15.03.05.05_multi_TD01, and Ac18 ac18_kf_V15.03.05.19(6318_)_cn devices allows remote unauthenticated attackers to read arbitrary files via a cgi-bin/luci/request?op=1&path= URI that uses directory traversal sequences after a /usb/ substring.
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Analysis
by VulDB Data Team • 12/10/2019
The CVE-2017-16936 vulnerability represents a critical directory traversal flaw affecting multiple Shenzhen Tenda wireless router models including AC9, AC15, and AC18 series. This vulnerability exists within the app_data_center component of the firmware, specifically in the web interface handling of file paths. The flaw allows remote unauthenticated attackers to access arbitrary files on the device by manipulating the URI parameter through the cgi-bin/luci/request?op=1&path= endpoint. The vulnerability is particularly concerning as it operates without requiring any authentication credentials, making it accessible to anyone on the network or even externally if the device is exposed to the internet.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization within the firmware's web server component. When the system processes the path parameter following the /usb/ substring, it fails to properly validate or sanitize user-supplied input, allowing attackers to inject directory traversal sequences such as ../ or ..\.. This oversight creates a path traversal condition where malicious actors can navigate beyond the intended directory boundaries and access sensitive system files, configuration data, or even system binaries that should remain protected. The vulnerability specifically targets the luci web interface framework used by these devices, which is designed to provide a user-friendly management portal but becomes a vector for unauthorized file access due to insufficient security controls.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to sensitive system data that could be exploited for further attacks. Attackers can retrieve configuration files that may contain administrative credentials, network settings, or other sensitive information that could be used for privilege escalation or lateral movement within a network. The vulnerability affects multiple firmware versions across different device models, indicating a widespread issue within the Tenda product line that could compromise numerous devices in both residential and commercial environments. This creates a significant risk for organizations that deploy these devices without proper network segmentation or security monitoring in place, as the vulnerability could be exploited from outside the local network if the devices are exposed to the internet.
Security professionals should consider this vulnerability in the context of the CWE-22 weakness category, which specifically addresses directory traversal attacks and improper input validation. The ATT&CK framework would classify this as a technique for privilege escalation and information gathering, as attackers can leverage the vulnerability to obtain system information that could be used to plan more sophisticated attacks. Organizations should implement immediate mitigations including firmware updates from Tenda, network segmentation to isolate affected devices, and monitoring for suspicious traffic patterns. The vulnerability also highlights the importance of secure coding practices and input validation in embedded systems, particularly in network infrastructure devices where unauthorized access could have severe consequences for network security and data integrity.