CVE-2026-51738 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the LoadDefSettings function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to reset the device configuration and reboot the device 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 management interface. Specifically, the LoadDefSettings function lacks proper authentication checks or authorization validation when processing incoming requests. This architectural flaw allows unauthenticated actors to interact with sensitive administrative functions that should be restricted to authorized users only. The vulnerability is exploitable remotely over HTTP by sending a specifically crafted POST request to the endpoint /cgi-bin/cstecgi.cgi, which serves as the gateway for executing various configuration commands on the device.
From a technical perspective, this issue stems from insufficient input validation and missing security controls in the CGI script handling routine. When an attacker submits a malicious payload targeting the LoadDefSettings function, the system fails to verify whether the requester possesses valid administrative credentials or session tokens. Consequently, the router proceeds to execute the command as if it originated from a legitimate administrator. This bypass of authentication mechanisms is particularly dangerous because it enables remote code execution at the configuration level without any prior login requirement. The ability to reset device settings and trigger reboots remotely undermines the fundamental integrity and availability guarantees expected in network infrastructure devices.
The operational impact of this vulnerability is severe, affecting both confidentiality and availability aspects of security. By resetting the device configuration, an attacker can erase custom firewall rules, Wi-Fi passwords, port forwarding configurations, and other critical network settings. This effectively returns the router to its factory default state, potentially exposing internal networks that were previously protected by specific security policies. Furthermore, the ability to reboot the device remotely introduces a significant availability risk. An adversary could exploit this feature to launch denial-of-service attacks against connected devices or disrupt business operations requiring stable internet connectivity. The combination of configuration reset and forced reboots creates a scenario where network stability is compromised while sensitive data may be exposed due to weakened security postures resulting from the factory reset.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-284, which describes Improper Access Control, specifically highlighting failures in enforcing authorization policies for critical functions. Additionally, it maps to MITRE ATT&CK technique T1531, indicating Account Manipulation through the alteration of account properties or configuration states that affect system behavior. The exploitation vector corresponds to remote attack paths typical of IoT and networking equipment vulnerabilities where management interfaces are exposed without adequate protection layers such as Web Application Firewalls (WAF) or strict API authentication protocols.
To mitigate this risk, immediate firmware updates provided by TOTOLINK should be applied if available for the affected model and version. Administrators must ensure that all devices running vulnerable firmware versions are patched to incorporate fixes for access control validation in CGI scripts. In environments where patching is not immediately feasible, network segmentation strategies can help isolate management interfaces from untrusted networks. Implementing strict firewall rules that restrict access to /cgi-bin/cstecgi.cgi only from trusted IP addresses or administrative subnets provides an additional layer of defense. Regular audits of router configurations and monitoring for unusual POST requests targeting configuration endpoints can also aid in early detection of exploitation attempts.