Signal K Server: Unauthenticated Source Priorities Manipulation
Date: 2026-04
Affected: npm/signalk-server
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-33951
CWE: CWE-284
CWE-306
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N)

## Summary The SignalK Server exposes an unauthenticated HTTP endpoint that allows remote attackers to modify navigation data source priorities. This endpoint, accessible via `PUT /signalk/v1/api/sourcePriorities`, does not enforce authentication or authorization checks and directly assigns user-controlled input to the server configuration. As a result, attackers can influence which GPS, AIS, or other sensor data sources are trusted by the system. The changes are immediately applied and persisted to disk, allowing the manipulation to survive server restarts. ### Affected Component - **File**: `src/serverroutes.ts` - **Endpoint**: `PUT /signalk/v1/api/sourcePriorities` (also accessible at `/skServer/sourcePriorities`) - **Lines**: 1064-1076 - **Function**: Source priorities configuration handler ### Vulnerable Code ```typescript // src/serverroutes.ts - Lines 1064-1076 app.put( `${SERVERROUTESPREFIX}/sourcePriorities`, (req: Request, res: Response) => { app.config.settings.sourcePriorities = req.body app.activateSourcePriorities() writeSettingsFile(app, app.config.settings, (err: any) => { if (err) { res .status(500) .send('Unable to save to sourcePrefences in settings file') } else { res.json({ result: 'ok' }) } }) } ) ``` ## Vulnerability Characteristics **Missing Authentication**: The endpoint has zero authentication middleware, allowing unauthenticated access from any network-adjacent attacke


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Architectural layers (MAESTRO):