CVE-2026-51667 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the getWiFiIpMacTable function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain Wi-Fi client MAC-to-IP mappings via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/31/2026
The vulnerability identified in TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the device's web management interface. Specifically, the flaw resides in the getWiFiIpMacTable function, which is exposed through the Common Gateway Interface script located at /cgi-bin/cstecgi.cgi. This architectural design allows unauthenticated users to interact with sensitive administrative functions that should strictly require valid authentication credentials. By sending a crafted POST request to this endpoint, an attacker can bypass standard security controls and retrieve internal network mapping data without prior authorization.
From a technical perspective, the core issue is an improper implementation of access control checks within the CGI script handler. The function getWiFiIpMacTable is designed to return a table correlating Media Access Control addresses with Internet Protocol addresses for connected Wi-Fi clients. In a secure configuration, this operation would be gated behind session validation or token verification processes that ensure only authenticated administrators can execute such queries. However, in the affected firmware version, these checks are either absent or incorrectly implemented, allowing any network user who has reachability to the router's management interface to invoke the function directly via HTTP POST requests. This lack of enforcement transforms a privileged administrative operation into an unauthenticated information disclosure vector.
The operational impact of this vulnerability is significant for both residential and small business networks relying on TOTOLINK hardware. The primary consequence is the unauthorized acquisition of Wi-Fi client MAC-to-IP mappings, which constitutes a severe privacy violation and facilitates further network reconnaissance. An attacker can use this data to build an accurate map of all devices connected to the local area network, identifying their unique identifiers and current IP assignments. This information serves as critical intelligence for subsequent attacks, such as ARP spoofing, man-in-the-middle attacks, or targeted exploitation of specific client vulnerabilities based on known device types associated with certain MAC address prefixes. Furthermore, exposing internal IP structures aids in lateral movement within the network segment.
This vulnerability aligns closely with Common Weakness Enumeration category CWE-284, which describes Improper Access Control, specifically where access control is not enforced for a critical function. Additionally, from an offensive security perspective as defined by the MITRE ATT&CK framework, this behavior corresponds to Discovery techniques involving Network Service Scanning and potentially Account Manipulation if combined with other exploits. The ability to enumerate connected devices without authentication undermines the fundamental principle of least privilege and compromises the confidentiality integrity of network topology data.
To mitigate this risk, users must immediately update their TOTOLINK T6 routers to a firmware version that addresses this access control flaw. If an updated patch is not yet available from the vendor, temporary mitigation strategies include restricting physical or remote access to the router's management interface by configuring firewall rules to allow only trusted IP addresses to reach port 80 and 443 on the device. Disabling the web management interface entirely when it is not in use also reduces the attack surface significantly. Administrators should ensure that default passwords are changed and that WPA2 or WPA3 encryption is enabled for Wi-Fi access, although these measures do not directly prevent exploitation of this specific CGI endpoint if network-level access to the router's LAN IP is possible. Regular monitoring of administrative logs can also help detect attempts to exploit such unauthenticated endpoints.