CVE-2026-51740 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the killProcess function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to terminate critical services 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 the killProcess function within TOTOLINK T6 firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms, specifically classified under CWE-284 Improper Access Control. This flaw resides in the device's web management interface, where the endpoint /cgi-bin/cstecgi.cgi processes POST requests without adequately verifying the authentication status or privilege level of the requesting user. The function is designed to terminate specific system services, but due to insufficient validation logic, it accepts commands from unauthenticated sources. An attacker who can reach this network service over HTTP does not need valid credentials to execute these termination commands, effectively bypassing any intended security boundaries that should restrict such administrative actions to authorized personnel only.
From a technical perspective, the exploitation of this vulnerability involves sending a specifically crafted POST request to the targeted CGI script. The payload typically includes parameters that instruct the killProcess function to target critical system daemons or services essential for the router's operation and network stability. Because the server-side logic fails to check session tokens, cookies, or other authentication indicators before processing the command, any entity with network connectivity to port 80 can trigger this action. This lack of authorization checks allows remote unauthenticated attackers to disrupt the normal functioning of the device by stopping services that maintain routing tables, DHCP leases, firewall rules, or wireless access point operations.
The operational impact of this vulnerability is severe and directly affects the availability component of the CIA triad. By terminating critical services, an attacker can cause a denial-of-service condition against both the managed router itself and potentially other devices on the local network that rely on its services for connectivity. For instance, stopping the DHCP service would prevent new clients from obtaining IP addresses, while halting DNS or routing processes could isolate segments of the network. This disruption degrades the reliability of the home or small office network infrastructure, leading to loss of productivity and potential security gaps if firewall-related services are compromised. Furthermore, such instability may force a reboot of the device, which can lead to data loss in volatile memory or trigger recovery modes that might expose further vulnerabilities depending on the implementation details.
This vulnerability aligns with MITRE ATT&CK technique T1529 System Shutdown/Reboot, where adversaries disrupt availability by stopping system processes. It also reflects common patterns found in CWE-732 Incorrect Permission Assignment for Critical Resource, as the resource (the killProcess function) is assigned permissions that are too broad relative to its sensitive nature. The root cause lies in the development lifecycle of embedded web interfaces, where convenience often overrides security, leading developers to expose administrative functions without proper gatekeeping mechanisms like session validation or role-based access control checks.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided firmware updates that patch the access control logic within the killProcess function. Administrators should ensure their TOTOLINK T6 devices are running a version of firmware where authentication is strictly enforced before any process termination commands are processed. In cases where immediate patching is not possible, network-level controls can provide temporary relief by restricting access to /cgi-bin/cstecgi.cgi through firewall rules or VLAN segmentation, ensuring that only trusted management stations can interact with the device's administrative interface. Additionally, disabling remote management features if they are not required reduces the attack surface available to external unauthenticated attackers. Regular security audits and penetration testing of embedded devices should include checks for improper access control on all exposed CGI endpoints to prevent similar issues in future deployments.