CVE-2026-51722 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiRepeaterCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to repoint the device to an attacker-controlled upstream Wi-Fi 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 routers running 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 setWiFiRepeaterCfg function, which is designed to configure wireless repeater settings but lacks proper authentication checks for certain operations. This misconfiguration allows unauthenticated attackers who have network-level connectivity to the router’s administrative interface to execute arbitrary commands that alter fundamental networking parameters without providing valid credentials. The attack vector involves sending a specially crafted POST request to the /cgi-bin/cstecgi.cgi endpoint, which serves as the primary gateway for executing configuration changes on these devices. By exploiting this weakness, an adversary can effectively hijack the router’s role in the network topology by redirecting its upstream Wi-Fi connection to access points controlled by the attacker rather than legitimate networks.
From a technical perspective, this vulnerability is classified under CWE-284 Improper Access Control and aligns with MITRE ATT&CK technique T1506.003, which involves Web Session Manipulation or misconfiguration of authentication mechanisms in web applications. The root cause lies in the application logic failing to verify user privileges before processing sensitive configuration changes. In many embedded router architectures, certain CGI scripts are intended for administrative use only but are inadvertently exposed to unauthenticated users due to incomplete role-based access control checks. When an attacker sends a POST request with specific parameters pointing to their own Wi-Fi network credentials or SSID, the device accepts and applies these settings immediately. This bypasses standard security protocols that should require authentication tokens or session cookies for any modification of wireless infrastructure settings.
The operational impact of this vulnerability is severe, as it enables man-in-the-middle attacks at a foundational level. By repointing the router to an attacker-controlled upstream Wi-Fi network, all traffic passing through the device can be intercepted, modified, or dropped by the adversary. This compromises confidentiality and integrity for any user connected to the local area network behind the compromised router. Attackers can perform credential harvesting, inject malicious content into web pages viewed by users, or monitor sensitive communications such as banking transactions or personal data exchanges. Furthermore, because this change affects the upstream connection, it may also disrupt legitimate internet access until the configuration is manually corrected via a physical reset or authenticated administrative session if one remains available.
Mitigation strategies must address both immediate remediation and long-term security posture improvements. The most effective solution is to apply firmware updates provided by TOTOLINK that patch this specific access control flaw, ensuring that all CGI endpoints enforce strict authentication checks before executing configuration changes. In the absence of an official update, administrators should restrict physical and network access to the router’s management interface by changing default passwords, disabling remote administration features if not required, and placing the device behind a firewall with rules limiting exposure to trusted IP addresses only. Additionally, implementing network segmentation can limit the blast radius of such compromises, ensuring that even if one device is repointed, lateral movement within the internal network remains constrained. Regular audits of router configurations and monitoring for unusual changes in upstream connection settings are also recommended to detect potential exploitation attempts early.