Description

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.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.1",
  "pubDate": "2026-08-19T15:18:01.943Z",
  "pubdate": "2026-08-19T15:18:01.943Z",
  "executiveSummary": "Cudy WR3000 version 2.0 running firmware prior to 2.5.24 contains a critical hard-coded cryptographic secret vulnerability within the Mosquitto MQTT broker authentication plugin. The vulnerability allows unauthenticated remote attackers to extract the hard-coded JSON Web Token (JWT) HMAC signing secret directly from the firmware image. Armed with this static cryptographic material, attackers can craft arbitrary, cryptographically valid JWT tokens and bypass authentication mechanisms entirely against the MQTT broker. The business impact includes full compromise of the device's mesh networking interface and potential unauthorized network manipulation. The risk implications are severe, as exploitation requires zero prior authentication, relying solely on static analysis of publicly available firmware binaries to extract the signing key. Attackers possessing the forged tokens gain unauthorized administrative or operational access to sensitive broker communications and underlying mesh services, threatening overall network integrity and device confidentiality.",
  "technicalDetails": "The vulnerability resides in the Mosquitto MQTT broker's authentication plugin implemented on the Cudy WR3000 2.0 running firmware before 2.5.24. The root cause of the flaw is the inclusion of a static, hard-coded HMAC signing secret used for generating and verifying JSON Web Tokens (JWT) within the authentication workflow. Because the cryptographic secret is hard-coded directly into the compiled binaries or configuration files packaged within the firmware image, it lacks entropy and dynamic per-device generation.\nThe step-by-step attack flow begins with reconnaissance, where an unauthenticated attacker acquires the target firmware image for the Cudy WR3000 version 2.0 (specifically prior to firmware version 2.5.24). Utilizing standard firmware extraction and reverse engineering utilities, the attacker unpacks the filesystem and locates the Mosquitto MQTT broker authentication plugin or associated binary modules. Through string extraction or disassembly techniques, the attacker identifies and extracts the hard-coded JWT HMAC signing secret.\nWith the valid HMAC secret retrieved, the attack transitions to active exploitation. The attacker constructs arbitrary JSON Web Tokens, specifying custom payload claims and signing the payload using the extracted HMAC secret. Because the Mosquitto MQTT broker authentication plugin validates incoming JWT signatures against the identical hard-coded secret embedded in the firmware, the broker cryptographically accepts the forged tokens as authentic.\nThe attacker then transmits the forged JWT token as part of the authentication handshake to the Mosquitto MQTT broker running on the device. Upon successful validation, the attacker is granted unauthorized access to the device's internal mesh networking interface without supplying any legitimate credentials. Privilege requirements for this phase are strictly none, as the vulnerability is exploitable by unauthenticated network entities capable of reaching the MQTT broker. Post-exploitation impact encompasses unauthorized control, monitoring, and interaction with the device's mesh networking architecture, exposing the local network topology and connected nodes to further malicious manipulation."
}