CVE-2026-51750 in TOTOLINK
Summary
by MITRE • 09/01/2026
Incorrect access control in the updatePriChannel function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to rescan and switch the primary mesh channel via sending a crafted MQTT message to the cs_broker component.
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Analysis
by VulDB Data Team • 09/01/2026
The vulnerability identified in TOTOLINK T6 firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the device's mesh networking subsystem. Specifically, the flaw resides in the updatePriChannel function, which is responsible for managing and switching the primary communication channel of the wireless mesh network. This component interacts with an MQTT broker service known as cs_broker to receive configuration updates or status changes from connected devices or management interfaces. The core technical deficiency lies in the absence of proper authentication checks before executing this sensitive administrative operation. Consequently, any actor capable of reaching the MQTT endpoint on the device can invoke this function without providing valid credentials, effectively bypassing intended security boundaries that should restrict such actions to authorized administrators only.
From a technical perspective, this vulnerability allows unauthenticated remote attackers to manipulate the network topology by forcing a rescan and subsequent switch of the primary mesh channel. By sending a specifically crafted MQTT message to the cs_broker component, an attacker can trigger the updatePriChannel routine without authorization. This capability disrupts the stability of the wireless environment because changing the primary channel often causes temporary disconnections for all devices associated with the mesh network as they attempt to reassociate on the new frequency. Furthermore, if the attacker selects a specific or maliciously chosen channel, it could facilitate interference attacks or degrade overall network performance intentionally. The exploitation does not require prior authentication, making it particularly dangerous in environments where the MQTT broker is exposed to untrusted networks or lacks sufficient isolation from user-facing interfaces.
The operational impact of this vulnerability extends beyond simple service disruption. An attacker with knowledge of the device's internal architecture could potentially use this flaw as a stepping stone for further exploitation. For instance, by repeatedly forcing channel switches, an attacker can create a persistent denial-of-service condition that degrades network availability and user experience. Additionally, if the mesh networking protocol relies on specific security parameters tied to the primary channel configuration, manipulating these settings might weaken other aspects of the device's defense posture or expose additional attack surfaces related to key management and encryption protocols associated with the new channel state. This aligns closely with CWE-284, which describes Improper Access Control, as the system fails to enforce proper authorization policies for a critical administrative function.
In terms of threat modeling, this vulnerability maps directly to MITRE ATT&CK techniques involving unauthorized configuration changes and potential disruption of availability. The ability to alter network parameters remotely without authentication is characteristic of attacks aimed at destabilizing infrastructure or preparing for more sophisticated intrusions where control over the communication channel provides leverage for man-in-the-middle scenarios or eavesdropping opportunities if encryption keys are regenerated improperly during the transition. Security researchers should note that MQTT brokers often operate with varying levels of security hardening, and this incident highlights the risk of exposing internal management protocols to unauthenticated access even in consumer-grade networking equipment designed for ease of use rather than robust enterprise-level security.
Mitigation strategies must focus on immediate remediation through vendor-provided patches if available, as updating the firmware is the most effective way to address code-level flaws such as missing authentication checks within specific functions like updatePriChannel. In the interim, network administrators should isolate the MQTT broker service from untrusted networks by implementing strict firewall rules that restrict access to trusted management subnets only. Additionally, enabling mutual TLS or other strong authentication mechanisms for all MQTT clients can prevent unauthorized entities from sending commands to the cs_broker component. Regular security audits of IoT device configurations and adherence to industry standards like CWE-284 during development phases are essential to preventing similar access control failures in future firmware releases.