CVE-2025-68620

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.

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.

SignalK Server exposes 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.

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.

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:

1. 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.

2. 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.

Affected Code

File: src/events.ts (lines 40-43)

Object.keys(app.lastServerEvents).forEach((propName) => {
  spark.write(app.lastServerEvents[propName])
})

All cached server events, including ACCESS_REQUEST, are sent to any connected WebSocket client without permission checks.

File: src/tokensecurity.js (lines 946-948)

strategy.getAccessRequestsResponse = () => {
  return filterRequests('accessRequest', 'PENDING')
}

This function returns all pending requests with full details, which is then broadcast as a server event.

File: src/requestResponse.js (lines 108-135)

function createReply(request, state, props) {
  const reply = {
    state: state,
    requestId: request.requestId
  }

  if (request.updateCb) {
    props.forEach((prop) => {
      if (typeof request[prop] !== 'undefined') {
        reply[prop] = request[prop]  // Includes 'token' when approved
      }
    })
  }
  return reply
}

When an access request transitions to COMPLETED state with APPROVED permission, the token is included in the reply object.

File: src/interfaces/rest.js (endpoint registration)

The /signalk/v1/access/requests/:id endpoint uses readonly authentication, allowing unauthenticated access when allow_readonly is true.

Impact

An attacker can obtain any JWT token issued by the server without authentication. By exploiting the social engineering vulnerability to request admin permissions, they receive a fully privileged admin token granting access to all protected endpoints including package installation, effectively bypassing authentication entirely. Additionally, attackers can hijack legitimate device credentials by stealing tokens intended for real devices.

PoC

import json, websocket, requests, time

TARGET_IP, TARGET_PORT = "localhost", 3000
TARGET_WS = f"ws://{TARGET_IP}:{TARGET_PORT}"
TARGET_HTTP = f"http://{TARGET_IP}:{TARGET_PORT}"

def…

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.

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.

SignalK Server exposes 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.

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.

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:

1. 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.

2. 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.

Affected Code

File: src/events.ts (lines 40-43)

Object.keys(app.lastServerEvents).forEach((propName) => {
  spark.write(app.lastServerEvents[propName])
})

All cached server events, including ACCESS_REQUEST, are sent to any connected WebSocket client without permission checks.

File: src/tokensecurity.js (lines 946-948)

strategy.getAccessRequestsResponse = () => {
  return filterRequests('accessRequest', 'PENDING')
}

This function returns all pending requests with full details, which is then broadcast as a server event.

File: src/requestResponse.js (lines 108-135)

function createReply(request, state, props) {
  const reply = {
    state: state,
    requestId: request.requestId
  }

  if (request.updateCb) {
    props.forEach((prop) => {
      if (typeof request[prop] !== 'undefined') {
        reply[prop] = request[prop]  // Includes 'token' when approved
      }
    })
  }
  return reply
}

When an access request transitions to COMPLETED state with APPROVED permission, the token is included in the reply object.

File: src/interfaces/rest.js (endpoint registration)

The /signalk/v1/access/requests/:id endpoint uses readonly authentication, allowing unauthenticated access when allow_readonly is true.

Impact

An attacker can obtain any JWT token issued by the server without authentication. By exploiting the social engineering vulnerability to request admin permissions, they receive a fully privileged admin token granting access to all protected endpoints including package installation, effectively bypassing authentication entirely. Additionally, attackers can hijack legitimate device credentials by stealing tokens intended for real devices.

PoC

import json, websocket, requests, time

TARGET_IP, TARGET_PORT = "localhost", 3000
TARGET_WS = f"ws://{TARGET_IP}:{TARGET_PORT}"
TARGET_HTTP = f"http://{TARGET_IP}:{TARGET_PORT}"

def…