CVE-2026-51744 in TOTOLINK
Summary
by MITRE • 09/01/2026
Incorrect access control in the recv_mesh_info_sync function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to force mesh configuration synchronization from an attacker-controlled host 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 router 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 recv_mesh_info_sync function, which is responsible for processing synchronization requests between mesh nodes to maintain consistent network topology and configuration states across multiple devices. This component interacts with an internal message broker service known as cs_broker, which utilizes MQTT (Message Queuing Telemetry Transport) protocol for communication. The core issue stems from a lack of proper authentication or authorization checks when handling incoming messages intended for this synchronization process. Consequently, the system fails to verify whether the source host initiating the mesh configuration sync request possesses valid credentials or legitimate administrative privileges within the local network environment.
From a technical perspective, an unauthenticated attacker positioned on the same local area network can exploit this weakness by crafting and transmitting specific MQTT payloads directly to the cs_broker component. By manipulating these messages, the attacker can force the router to accept configuration data from any arbitrary host under their control rather than only from trusted mesh nodes or authorized management interfaces. This bypasses standard security boundaries that should restrict such sensitive administrative operations exclusively to authenticated users or pre-authorized devices. The ability to inject false synchronization commands allows the adversary to alter critical network parameters, potentially disrupting connectivity, redirecting traffic, or destabilizing the entire mesh infrastructure depending on the content of the crafted message.
The operational impact of this vulnerability is significant for both residential and small business environments relying on TOTOLINK mesh systems for seamless Wi-Fi coverage. Successful exploitation could lead to a denial of service condition if the attacker forces conflicting configuration updates that cause nodes to disconnect or fail to associate properly. Furthermore, it poses severe risks to network integrity and confidentiality. An attacker might manipulate routing tables or security settings embedded in the sync data, effectively taking control over how devices communicate within the mesh. This could facilitate man-in-the-middle attacks, traffic interception, or further lateral movement into other connected systems on the private network segment. The absence of authentication for such a high-privilege operation fundamentally undermines the trust model required for secure distributed networking architectures.
This flaw aligns with Common Weakness Enumeration (CWE) category CWE-287, which describes Improper Authentication, as well as CWE-862, Missing Authorization, since the system does not verify if the actor has permission to execute the sync function. In terms of offensive security frameworks, this vulnerability maps closely to MITRE ATT&CK technique T1098, specifically SSH Unauthorized Access or similar protocol-based unauthorized access vectors where attackers exploit weak authentication controls to gain footholds and manipulate configurations remotely. It also relates to lateral movement tactics as it allows an attacker to influence the state of multiple connected devices simultaneously through a single broadcast-style message injection.
To mitigate this risk, users should immediately update their TOTOLINK T6 firmware to the latest version released by the vendor, which likely includes patches for these access control deficiencies in the mesh synchronization logic. Until such updates are applied or available, network administrators can implement compensating controls at the infrastructure level. This includes configuring firewall rules on upstream routers or switches to restrict MQTT traffic (typically port 1883) from untrusted hosts to the router's management interface and internal services. Isolating IoT devices into separate VLANs with strict access control lists further limits an attacker's ability to reach the cs_broker component directly. Additionally, disabling mesh features if they are not strictly necessary reduces the attack surface associated with this specific function. Regular monitoring of network logs for unusual MQTT activity can also aid in early detection of exploitation attempts.