Signal K Server: Unauthenticated Source Priorities Manipulation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-33951: 0.32% estimated exploitation activity in the next 30 days; percentile 25.30 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 Vulnerability Characteristics Missing Authentication: The endpoint has zero authentication middleware, allowing unauthenticated access from any network-adjacent attacker. Direct Configuration Assignment:…

Published by the source

3 Apr 2026, 21:42 UTC

Last modified by the source

6 Apr 2026, 23:34 UTC

Source last checked

26 Oct 2026, 12:47 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gfmv-vh34-h2x5

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gfmv-vh34-h2x5

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# Patch Next advisory brief: CVE-2026-33951

Advisory: Signal K Server: Unauthenticated Source Priorities Manipulation
IDs: CVE-2026-33951, GHSA-gfmv-vh34-h2x5
Record: https://patchnext.com/advisories/cve-2026-33951 (revision 3, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: signalk-server 2.24.0-beta.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm signalk-server: affected < 2.24.0-beta.1; fixed in 2.24.0-beta.1

## Suggested inspection (read-only)
- `npm ls signalk-server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on signalk-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gfmv-vh34-h2x5 (OSV record GHSA-gfmv-vh34-h2x5 lists affected ranges: npm signalk-server >=0 <2.24.0-beta.1 (fixed))
- Verified: https://github.com/advisories/GHSA-gfmv-vh34-h2x5 (GitHub-reviewed advisory GHSA-gfmv-vh34-h2x5 lists affected ranges: npm signalk-server >=0 <2.24.0-beta.1)

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