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Critical severityOSV Advisory· Published Jan 1, 2026· Updated Jan 2, 2026

Signal K Server vulnerable to JWT Token Theft via WebSocket Enumeration and Unauthenticated Polling

CVE-2025-68620

Description

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.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
signalk-servernpm
< 2.19.02.19.0

Affected products

1

Patches

1
221aff6cd89c

Merge commit from fork

https://github.com/SignalK/signalk-serverTeppo KurkiDec 27, 2025via ghsa
commit
2 files changed · +30 −6
  • src/events.ts+13 −0 modified
    @@ -10,6 +10,12 @@ export function startEvents(
   onEvent: (data: any) => void,
   eventsFromQuery = ''
 ) {
+  if (
+    !app.securityStrategy.isDummy() &&
+    !app.securityStrategy.hasAdminAccess?.(spark.request)
+  ) {
+    return
+  }
   const events = eventsFromQuery.split(',')
   events.forEach((event) => {
     app.on(event, (data: any) => onEvent({ event, data }))
@@ -22,6 +28,13 @@ export function startServerEvents(app: any, spark: any, onServerEvent: any) {
   spark.onDisconnects.push(() => {
     app.removeListener('serverevent', onServerEvent)
   })
+
+  if (app.securityStrategy.hasAdminAccess?.(spark.request)) {
+    app.on('serverAdminEvent', onServerEvent)
+    spark.onDisconnects.push(() => {
+      app.removeListener('serverAdminEvent', onServerEvent)
+    })
+  }
   try {
     spark.write({
       type: 'VESSEL_INFO',
  • src/tokensecurity.js+17 −6 modified
    @@ -136,6 +136,15 @@ module.exports = function (app, config) {
     }
   }
 
+  function hasAdminAccess(req) {
+    return (
+      req.skIsAuthenticated &&
+      req.skPrincipal &&
+      req.skPrincipal.permissions === 'admin'
+    )
+  }
+  strategy.hasAdminAccess = hasAdminAccess
+
   function writeAuthenticationMiddleware() {
     return function (req, res, next) {
       if (!getIsEnabled()) {
@@ -161,10 +170,12 @@ module.exports = function (app, config) {
         return next()
       }
 
+      if (hasAdminAccess(req)) {
+        return next()
+      }
+
       if (req.skIsAuthenticated && req.skPrincipal) {
-        if (req.skPrincipal.permissions === 'admin') {
-          return next()
-        } else if (req.skPrincipal.identifier === 'AUTO' && redirect) {
+        if (req.skPrincipal.identifier === 'AUTO' && redirect) {
           res.redirect('/@signalk/server-admin-ui/#/login')
         } else {
           handlePermissionDenied(req, res, next)
@@ -394,11 +405,11 @@ module.exports = function (app, config) {
   }
 
   strategy.allowRestart = function (req) {
-    return req.skIsAuthenticated && req.skPrincipal.permissions === 'admin'
+    return hasAdminAccess(req)
   }
 
   strategy.allowConfigure = function (req) {
-    return req.skIsAuthenticated && req.skPrincipal.permissions === 'admin'
+    return hasAdminAccess(req)
   }
 
   strategy.getLoginStatus = function (req) {
@@ -973,7 +984,7 @@ module.exports = function (app, config) {
   }
 
   function sendAccessRequestsUpdate() {
-    app.emit('serverevent', {
+    app.emit('serverAdminEvent', {
       type: 'ACCESS_REQUEST',
       from: CONFIG_PLUGINID,
       data: strategy.getAccessRequestsResponse()

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

5

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