Description

CyberPanel before 3.0.0 contains a hard-coded JWT secret vulnerability in the WebTerminal FastAPI SSH service that allows unauthenticated remote attackers to forge valid authentication tokens and obtain an interactive root shell via WebSocket on port 8888. Attackers can craft a forged JWT signed with the hardcoded secret value, specifying ssh_user=root, to authenticate to the terminal service without any valid credentials and receive a root shell.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-13T18:18:08.370Z",
  "pubdate": "2026-08-13T18:18:08.370Z",
  "executiveSummary": "CyberPanel versions before 3.0.0 suffer from a critical hard-coded JWT secret vulnerability residing within the WebTerminal FastAPI SSH service.\nThis architectural flaw allows unauthenticated remote attackers to mathematically forge valid JSON Web Tokens due to the predictable and statically compiled signing key.\nBy crafting a forged authentication token specifying the root user, malicious actors can bypass all access controls and achieve direct interactive root shell access via WebSocket on port 8888.\nThe risk implications are severe, as successful exploitation yields complete system compromise, arbitrary command execution, and total loss of confidentiality, integrity, and availability.\nAttacker capabilities require no prior authentication or valid user credentials, relying solely on network accessibility to the exposed terminal service.\nExploitation requirements are minimal, needing only the knowledge of the hard-coded secret to generate the cryptographic signature required by the FastAPI backend.",
  "technicalDetails": "The root cause of the vulnerability lies in the implementation of the WebTerminal FastAPI SSH service within CyberPanel before 3.0.0, where cryptographic tokens are signed using a static, hard-coded JSON Web Token (JWT) secret rather than a dynamically generated or securely managed instance-specific key.\nThe vulnerable component is the authentication middleware or validation routine handling incoming WebSocket upgrade requests and connection handshakes on network port 8888.\nBecause the secret key is hard-coded and distributed statically across installations, any remote attacker can inspect or reverse-engineer the application to extract the signing key.\nThe attack flow proceeds as follows: First, the attacker establishes network connectivity to port 8888 where the FastAPI SSH service listens for WebSocket connections. Second, instead of authenticating through standard credential validation, the attacker constructs a custom JSON Web Token payload. This payload explicitly specifies parameters such as ssh_user set to root. Third, the attacker signs this crafted payload using the extracted hard-coded JWT secret, generating a mathematically valid cryptographic signature that the verification routine will accept without question. Fourth, the attacker transmits the forged JWT to the WebTerminal service during the WebSocket handshake. Fifth, the service validates the signature against the hard-coded secret, evaluates the token as authentic, and maps the session to the requested root user. Finally, the service provisions an interactive root shell over the WebSocket connection, granting the attacker unrestricted administrative command execution capabilities.\nThe authentication requirements for this attack are entirely absent, as the vulnerability explicitly bypasses standard login procedures.\nThe privilege requirements to initiate the attack are zero, though the resulting post-exploitation impact grants the highest level of system privileges (root).\nNetwork exposure is defined by the exposure of port 8888 to untrusted networks, permitting remote exploitation over the wire.\nThe payload behavior involves supplying a manipulated claims set within a structurally standard JWT, successfully tricking the backend authorization logic into provisioning system resources reserved for administrative operators."
}