CVE-2026-51640 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getMeshNeighborTable function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain mesh neighbor information via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in the getMeshNeighborTable function within TOTOLINK T6 firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms, specifically categorized under CWE-284 Improper Access Control. This flaw permits unauthenticated remote attackers to retrieve sensitive mesh network topology data by interacting with the device's web interface. The attack vector involves sending a specially crafted POST request to the endpoint /cgi-bin/cstecgi.cgi, which serves as the gateway for executing various administrative and diagnostic functions on the router. Because the function does not adequately verify the authentication status or privilege level of the requesting user before processing the command, it exposes internal network configuration details that should remain restricted to authorized administrators only.
From a technical perspective, this vulnerability stems from insufficient validation checks within the CGI script handling mesh neighbor table queries. In typical secure implementations, functions that expose sensitive operational data such as routing tables or neighbor lists must enforce strict authentication protocols and role-based access controls. The absence of these safeguards allows any entity with network connectivity to the router's management interface to query this information without providing valid credentials. This lack of enforcement effectively bypasses the intended security boundary, turning a diagnostic feature into an unauthorized information disclosure channel.
The operational impact of this vulnerability is significant for organizations relying on mesh networking solutions provided by TOTOLINK devices. Mesh neighbor information typically includes details about connected nodes, their IP addresses, signal strengths, and routing paths within the local network area. Exposure of this data enables attackers to map the internal network structure with high precision. This reconnaissance phase can facilitate further attacks such as man-in-the-middle operations, targeted denial-of-service against specific mesh nodes, or lateral movement within the network once an initial foothold is gained. By understanding the topology and relationships between devices, adversaries can identify weak points in the security architecture that are not immediately visible through standard external scanning techniques.
This vulnerability aligns with several entries in the MITRE ATT&CK framework, particularly T1046 Network Service Discovery, where attackers enumerate services to map network infrastructure. It also relates to CWE-200 Information Exposure, as it involves the unauthorized disclosure of information that could be detrimental to security posture. The ability to gather mesh neighbor data without authentication underscores a fundamental gap in the device's security design, highlighting the need for rigorous input validation and access control checks on all CGI endpoints exposed to potentially untrusted networks.
Mitigation strategies should prioritize immediate patching if an updated firmware version is available from TOTOLINK that addresses this specific access control flaw. In environments where updating is not immediately feasible, network segmentation can help limit exposure by ensuring the management interface of these routers is only accessible from trusted administrative subnets rather than general user networks or public-facing interfaces. Additionally, implementing strict firewall rules to restrict POST requests to /cgi-bin/cstecgi.cgi to known administrator IP addresses can reduce the attack surface. Regular security audits and penetration testing focused on authentication bypasses in embedded device web interfaces are recommended to identify similar vulnerabilities before they can be exploited by malicious actors.