CVE-2026-51614 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getAccessDeviceCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain access-device policy and client state information via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/28/2026
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 management interface. Specifically, the flaw resides in the getAccessDeviceCfg function, which is exposed through the Common Gateway Interface script located at /cgi-bin/cstecgi.cgi. This endpoint is designed to handle configuration requests for network devices connected to the router, but it fails to enforce proper authentication checks before processing incoming data. As a result, any external or internal actor with network connectivity to the management interface can interact with this function without providing valid credentials. The attacker achieves access by sending a specifically crafted POST request to the vulnerable endpoint, exploiting the lack of session validation and privilege verification that should normally restrict such administrative operations to authorized users only.
From a technical perspective, this vulnerability is classified under CWE-284, which describes Improper Access Control, as well as CWE-306, Missing Authentication for Critical Function. The root cause lies in the application logic of the CGI script, where the getAccessDeviceCfg function processes requests without verifying if the requester has been authenticated or authorized to view sensitive configuration data. This oversight allows an unauthenticated attacker to retrieve detailed information about access-device policies and current client states. Access-device policies typically define rules governing how connected devices are treated by the network, such as bandwidth limits, firewall rules, or parental controls. Client state information includes details about active connections, IP addresses assigned via DHCP, MAC addresses of connected devices, and potentially signal strength or connection duration. The ability to extract this data provides a comprehensive view of the local network topology and security posture without needing to breach any encryption keys or bypass complex authentication protocols.
The operational impact of this vulnerability is significant for both residential and small business environments relying on TOTOLINK routers. By obtaining access-device policy configurations, an attacker can map out the intended security rules applied to various devices on the network. This information aids in identifying potential weaknesses, such as misconfigured firewall rules or disabled security features that protect specific clients. Furthermore, accessing client state data allows for passive reconnaissance of all devices currently connected to the Wi-Fi or wired LAN. An adversary could use this intelligence to plan targeted attacks against vulnerable IoT devices, perform man-in-the-middle attacks by spoofing MAC addresses if other controls are weak, or simply monitor user activity and network usage patterns. In a broader context, this exposure facilitates lateral movement within a private network, as the attacker gains valuable insights into device types, operating systems inferred from client identifiers, and network segmentation strategies that may be incorrectly configured.
This type of vulnerability aligns with several tactics in the MITRE ATT&CK framework for enterprise networks. It falls under Initial Access via Exploitation of Remote Services, specifically leveraging web application vulnerabilities to gain foothold or gather intelligence. The subsequent information gathering phase corresponds to T1087, Account Discovery and T1592, Gather Victim Host Information, as the attacker collects data about connected hosts and their configurations. Although this specific flaw does not directly allow code execution, it serves as a powerful reconnaissance tool that significantly lowers the barrier for further exploitation attempts against other services or devices on the same network segment.
Mitigation strategies must address both immediate remediation and long-term security hygiene. The primary solution is to apply the latest firmware update provided by TOTOLINK, which should include patches correcting the access control logic in the getAccessDeviceCfg function. If an updated firmware is not immediately available or applicable, administrators can mitigate risk by disabling remote management features if they are enabled on the router's WAN interface. Additionally, ensuring that the administrative web interface is only accessible from trusted internal network segments and enforcing strong, unique passwords for all user accounts reduces the attack surface. Network segmentation should also be considered to isolate critical IoT devices or sensitive workstations from general guest networks, limiting the blast radius if an attacker does manage to exploit this information disclosure vulnerability. Regular audits of connected clients and review of access policies can help detect any unauthorized changes resulting from such exploits.