CVE-2026-71960 in WR3000
Summary
by MITRE • 08/19/2026
Cudy WR3000 2.0 running firmware before 2.5.24 contains a hard-coded JWT HMAC signing secret vulnerability in the Mosquitto MQTT broker's authentication plugin that allows unauthenticated attackers to forge valid JWT tokens by extracting the secret from the firmware image. Attackers can use the extracted secret to craft arbitrary JWT tokens and authenticate to the MQTT broker without legitimate credentials, gaining unauthorized access to the device's mesh networking interface.
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Analysis
by VulDB Data Team • 08/19/2026
The vulnerability identified in Cudy WR3000 2.0 devices running firmware prior to version 2.5.24 represents a critical failure in cryptographic key management within the embedded IoT ecosystem. This flaw specifically affects the Mosquitto MQTT broker's authentication plugin, which relies on JSON Web Tokens (JWT) for securing communications over its mesh networking interface. The core technical deficiency lies in the implementation of the HMAC signing secret used to validate JWT signatures. Instead of generating a unique, random secret key during device initialization or provisioning, the firmware utilizes a hard-coded static value embedded directly into the binary image. This architectural decision violates fundamental security principles regarding dynamic key generation and secure storage, effectively rendering any cryptographic protection provided by JWT meaningless if an attacker can access the underlying file system or memory dump of the device.
From a technical perspective, this vulnerability allows for straightforward exploitation through firmware analysis. An adversary with physical access to the router or those who have previously compromised the device's administrative interface can extract the firmware image and perform static analysis to locate the hard-coded HMAC secret. Once extracted, this secret enables the attacker to forge valid JWT tokens without possessing any legitimate user credentials. By crafting a token signed with the known secret, the attacker can bypass the authentication mechanism entirely. This capability grants unauthorized access to the MQTT broker service, which serves as the backbone for device-to-device communication in the mesh network topology managed by the router. The ease of extracting this static key highlights a significant oversight in the development lifecycle where security testing failed to identify that hard-coded secrets are trivially discoverable using standard reverse engineering tools.
The operational impact of this vulnerability is severe, particularly given the role of the MQTT broker in IoT mesh networks. Successful exploitation allows an unauthenticated attacker to inject malicious messages into the network or intercept sensitive data transmitted between connected smart home devices and cloud services. Since the MQTT protocol often carries configuration commands, status updates, and potentially control signals for peripheral devices like lights, locks, or sensors, unauthorized access can lead to a wide range of adverse outcomes. These include denial of service by flooding the broker with invalid messages, manipulation of device states leading to physical security risks such as unlocking doors or disabling alarms, and potential pivoting into other segments of the local network if the MQTT integration exposes further attack surfaces. The compromise undermines the integrity and confidentiality guarantees that the mesh networking architecture is designed to provide.
This vulnerability aligns closely with CWE-798: Use of Hard-coded Credentials, a classification indicating the use of static authentication credentials in code rather than dynamic or user-provided secrets. Furthermore, from an offensive security perspective, this exploit technique maps to MITRE ATT&CK techniques related to Credential Access and Defense Evasion, specifically leveraging extracted artifacts for lateral movement within the IoT environment. To mitigate this risk, users must immediately update their Cudy WR3000 firmware to version 2.5.24 or later where the hard-coded secret has been replaced with a dynamically generated unique key per device. For organizations managing fleets of these devices, it is imperative to implement network segmentation to isolate IoT mesh networks from critical corporate infrastructure and monitor MQTT traffic for anomalies indicative of forged tokens until patches are applied.