Signal K Server is a server application that runs on a central hub in a boat. Versions prior to 2.19.0 expose two features that can be chained together to steal JWT authentication tokens without any prior authentication. The attack combines WebSocket-based request enumeration with unauthenticated polling of access request status. The first is Unauthenticated WebSocket Request Enumeration: When a WebSocket client connects to the SignalK stream endpoint with the `serverevents=all` query parameter, the server sends all cached server events including `ACCESS_REQUEST` events that contain details about pending access requests. The `startServerEvents` function iterates over `app.lastServerEvents` and writes each cached event to any connected client without verifying authorization level. Since WebSocket connections are allowed for readonly users (which includes unauthenticated users when `allow_readonly` is true), attackers receive these events containing request IDs, client identifiers, descriptions, requested permissions, and IP addresses. The second is Unauthenticated Token Polling: The access request status endpoint at `/signalk/v1/access/requests/:id` returns the full state of an access request without requiring authentication. When an administrator approves a request, the response includes the issued JWT token in plaintext. The `queryRequest` function returns the complete request object including the token field, and the REST endpoint uses readonly authentication, allowing unauthenticated access. An attacker has two paths to exploit these vulnerabilities. Either the attacker creates their own access request (using the IP spoofing vulnerability to craft a convincing spoofed request), then polls their own request ID until an administrator approves it, receiving the JWT token; or the attacker passively monitors the WebSocket stream to discover request IDs from legitimate devices, then polls those IDs and steals the JWT tokens when administrators approve them, hijacking legitimate device credentials. Both paths require zero authentication and enable complete authentication bypass. Version 2.19.0 fixes the underlying issues.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - Signal K Server is a server application that runs on a central hub in a boat. Versions prior to 2.19.0
    expose two features that can be chained together to steal JWT authentication tokens without any prior
    authentication. The attack combines WebSocket-based request enumeration with unauthenticated polling of
    access request status. The first is Unauthenticated WebSocket Request Enumeration: When a WebSocket client
    connects to the SignalK stream endpoint with the `serverevents=all` query parameter, the server sends all
    cached server events including `ACCESS_REQUEST` events that contain details about pending access requests.
    The `startServerEvents` function iterates over `app.lastServerEvents` and writes each cached event to any
    connected client without verifying authorization level. Since WebSocket connections are allowed for
    readonly users (which includes unauthenticated users when `allow_readonly` is true), attackers receive
    these events containing request IDs, client identifiers, descriptions, requested permissions, and IP
    addresses. The second is Unauthenticated Token Polling: The access request status endpoint at
    `/signalk/v1/access/requests/:id` returns the full state of an access request without requiring
    authentication. When an administrator approves a request, the response includes the issued JWT token in
    plaintext. The `queryRequest` function returns the complete request object including the token field, and
    the REST endpoint uses readonly authentication, allowing unauthenticated access. An attacker has two paths
    to exploit these vulnerabilities. Either the attacker creates their own access request (using the IP
    spoofing vulnerability to craft a convincing spoofed request), then polls their own request ID until an
    administrator approves it, receiving the JWT token; or the attacker passively monitors the WebSocket
    stream to discover request IDs from legitimate devices, then polls those IDs and steals the JWT tokens
    when administrators approve them, hijacking legitimate device credentials. Both paths require zero
    authentication and enable complete authentication bypass. Version 2.19.0 fixes the underlying issues.
    (CVE-2025-68620)

ID	Name	Product	Family	Severity
436540	SCA: security update for signalk-server (GHSA-fq56-hvg6-wvm5)	Tenable Cloud Security	SCA Checks	critical
436540	SCA: security update for signalk-server (GHSA-fq56-hvg6-wvm5)	Tenable Self-Hosted Container Security	SCA Checks	critical

Detections

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CVE-2025-68620

critical

Tenable Plugins

critical

critical