CVE-2026-51752 in TOTOLINK
Summary
by MITRE • 09/01/2026
Incorrect access control in the staticInfoSend function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to trigger static information reporting to the configured master 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 communication architecture. Specifically, the flaw resides in the staticInfoSend function, which is responsible for transmitting static system information to a configured master node or management server via MQTT protocol. The core technical deficiency lies in the absence of authentication requirements when invoking this specific function through the cs_broker component. This architectural oversight allows any entity with network connectivity to the device's message broker interface to initiate data transmission without providing valid credentials, effectively bypassing intended security boundaries that should restrict such operations to authorized administrators or trusted management systems only.
From a technical perspective, MQTT is commonly used in Internet of Things (IoT) environments for lightweight publish-subscribe messaging. In this specific implementation, the cs_broker component acts as an intermediary handling these messages. The vulnerability arises because the staticInfoSend function does not validate the identity or permissions of the sender before processing the request and transmitting sensitive device data. This lack of input validation regarding access control allows unauthenticated actors to craft malicious MQTT payloads that trigger the information disclosure routine. By sending a specifically crafted message, an attacker can force the router to package and send its static configuration details, hardware identifiers, network settings, or other proprietary system states to whatever master endpoint is configured in the device's firmware.
The operational impact of this vulnerability is significant for both privacy and security posture. The disclosure of static information often includes unique device identifiers such as MAC addresses, serial numbers, model specifics, and potentially current network configuration details like IP addresses, subnet masks, or DNS settings. This data can be leveraged by attackers to build detailed profiles of the target infrastructure, facilitating more targeted subsequent attacks. For instance, knowing the exact firmware version and hardware revision allows adversaries to search for known exploits specific to that variant. Furthermore, if the static information includes any embedded credentials or API keys intended for external management services, their exposure could lead to complete compromise of the device's remote administration capabilities. This aligns with CWE-269, which classifies this as an Improper Privilege Context issue where a user is granted privileges that are not appropriate for their role or authentication state.
In terms of threat modeling and attack classification, this vulnerability maps directly to ATT&CK technique T1078, Valid Accounts, specifically in the context of default or misconfigured credentials if such were present, but more accurately reflects T1539, Steal Web Session Cookies, adapted for IoT contexts where session tokens are often absent. More precisely, it falls under information gathering techniques similar to T1426, Network Device Discovery, as it aids in fingerprinting the device type and version. The exploitation vector is network-based (Network), requiring no physical access or prior authentication, which classifies it as a high-severity remote code execution precursor or data exfiltration vulnerability depending on the sensitivity of the static info sent.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. For administrators currently running this firmware version, the primary mitigation is to upgrade to a patched release where access control checks have been implemented in the cs_broker component for all sensitive functions including staticInfoSend. If an update is not immediately available, network segmentation should be employed to restrict MQTT broker port accessibility solely to trusted management subnets or IP addresses using firewall rules. Additionally, enabling TLS encryption on MQTT connections can prevent eavesdropping of the transmitted data, although it does not mitigate the unauthorized access itself. From a development standpoint, future firmware iterations must enforce strict authentication and authorization checks before executing any function that interacts with external brokers or transmits device state information. Implementing principle of least privilege ensures that only authenticated and authorized processes can trigger sensitive system operations, thereby closing this vector for unauthenticated exploitation.