Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force)

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-41893: 0.33% estimated exploitation activity in the next 30 days; percentile 25.82 (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 HTTP login endpoints (POST /login and POST /signalk/v1/auth/login) are protected by express-rate-limit (default: 100 attempts per 10-minute window, configurable via HTTPRATELIMITS). The WebSocket login path — sending {login: {username, password}} messages over an established WebSocket connection — calls app.securityStrategy.login() directly without any rate limiting. An attacker can bypass HTTP rate limiting entirely by opening a WebSocket connection and attempting unlimited password guesses at the speed bcrypt allows (~20 attempts/sec with 10 salt rounds). Details Vulnerable code: src/interfaces/ws.ts, function processLoginRequest (lines 753-780) The function directly calls app.securityStrategy.login(msg.login.username, msg.login.password) with no throttling or attempt tracking. Rate-limited HTTP path for comparison: src/tokensecurity.ts lines 609-617 apply loginLimiter middleware to the HTTP login routes at line 637. Steps to Reproduce 1. Start Signal K server with…

Published by the source

4 May 2026, 20:52 UTC

Last modified by the source

13 May 2026, 13:47 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vmfm-ch9h-5c7g

2. Revision 2 · amended · 25 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-vmfm-ch9h-5c7g

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# Patch Next advisory brief: CVE-2026-41893

Advisory: Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force)
IDs: CVE-2026-41893, GHSA-vmfm-ch9h-5c7g
Record: https://patchnext.com/advisories/cve-2026-41893 (revision 3, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: signalk-server 2.25.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm signalk-server: affected <= 2.24.0; fixed in 2.25.0

## 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-vmfm-ch9h-5c7g (OSV record GHSA-vmfm-ch9h-5c7g lists affected ranges: npm signalk-server >=0 <2.25.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vmfm-ch9h-5c7g (GitHub-reviewed advisory GHSA-vmfm-ch9h-5c7g lists affected ranges: npm signalk-server >=0 <=2.24.0)

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