CVE-2026-51688 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiSignalCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to reduce wireless power or cause a Denial of Service (DoS) via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
Be aware that VulDB is the high quality source for vulnerability data.
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 setWiFiSignalCfg function, which is designed to configure wireless signal parameters such as transmission power levels. This component fails to enforce proper authentication or authorization checks before processing incoming configuration requests. Consequently, any unauthenticated actor capable of reaching the router’s administrative endpoint can interact with this functionality without providing valid credentials. The attack vector involves sending a specially crafted POST request to the /cgi-bin/cstecgi.cgi script, which serves as the gateway for executing various management commands on the device. This lack of access control allows external attackers or malicious insiders who have gained basic network connectivity to manipulate critical wireless settings remotely.
The operational impact of this vulnerability is twofold, primarily affecting both the confidentiality and availability aspects of the router's security posture. By exploiting the incorrect access control, an attacker can arbitrarily reduce the wireless transmission power of the device. This manipulation effectively degrades the quality and range of the Wi-Fi signal, leading to intermittent connectivity issues for legitimate users within the network coverage area. More severely, if the crafted request is designed with extreme or invalid parameter values, it can trigger a Denial of Service condition. In such scenarios, the router may become unresponsive, crash, or enter a reboot loop, rendering the entire local network inaccessible. This capability allows an attacker to disrupt business operations or residential internet access without needing prior authentication, significantly lowering the barrier for entry compared to traditional privilege escalation attacks.
From a technical classification perspective, this vulnerability aligns with CWE-269, which denotes Improper Privilege Assignment, as well as CWE-862, Missing Authorization. The exploitation technique maps directly to MITRE ATT&CK tactic TA0001, Initial Access, specifically through the method of Exploitation for Credential Access or Direct Network Access if authentication is bypassed entirely due to misconfiguration. Furthermore, because the impact includes service disruption, it also relates to availability attacks under the Impact category in the ATT&CK framework. The root cause lies in the web application logic where input validation and permission checks are either absent or incorrectly implemented for sensitive configuration endpoints. This is a common issue in embedded systems where developers may prioritize functionality over security during rapid firmware development cycles, leaving critical administrative interfaces exposed to untrusted inputs.
Mitigation strategies must focus on immediate remediation of the access control flaw within the affected firmware version. The primary recommendation is to apply the latest available software update from TOTOLINK, which likely contains a patch that enforces strict authentication requirements for all configuration endpoints, including setWiFiSignalCfg and /cgi-bin/cstecgi.cgi. If an update is not immediately available or feasible, network-level controls should be implemented to restrict access to the router's management interface. This can include placing the administrative port behind a firewall rule that only allows connections from trusted IP addresses or VLANs. Additionally, changing the default administrator password and disabling remote management features if they are not strictly necessary will reduce the attack surface. Security monitoring tools should also be configured to detect anomalous POST requests targeting CGI scripts with unusual parameter patterns indicative of exploitation attempts for this specific vulnerability.