CVE-2026-41893: SignalK Signal K Server brute-force protection bypass in WebSocket login

CVE-2026-41893 · Severity: high · CVSS 7.5 · Published 2026-05-09

Signal K Server, a central hub used for marine data on boats, contains a security flaw in its login system. While standard web logins were protected against repeated password guessing, an alternative login method via WebSockets was not. This allows an attacker to attempt thousands of passwords in a short period to gain unauthorized access to the vessel's server.

Technologies: signalk-server (npm), Signal K Server. Vendors: npm, Signal K.

Quick answers

Is CVE-2026-41893 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-41893 being exploited in the wild.
How severe is CVE-2026-41893?
High severity, with a CVSS score of 7.5, published 9 May 2026.
Which products and versions are affected?
signalk-server (npm) <= 2.24.0, SEMVER:introduced=0,fixed=2.25.0; Signal K Server < 2.25.0.
Is there a fix for CVE-2026-41893?
Yes. signalk-server (npm): upgrade to 2.25.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-41893 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-41893?
Check whether you run signalk-server (npm) or Signal K Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • signalk-server (npm): upgrade to 2.25.0 or later
    npm install signalk-server@2.25.0

Technical details

Signal K Server prior to version 2.25.0 implements rate limiting for HTTP login endpoints (POST /login) using express-rate-limit, but fails to apply similar protections to the WebSocket login path. An attacker can establish a WebSocket connection and send '{login: {username, password}}' messages to call the internal login strategy directly. Because this path bypasses the HTTP middleware, it allows for unthrottled brute-force attempts at the speed of the underlying bcrypt hash verification (approximately 20 attempts per second). The vulnerability is addressed in version 2.25.0 by introducing a shared LoginRateLimiter that tracks attempts across both HTTP and WebSocket protocols.

Affected products

  • SignalK Signal K Server < 2.25.0

Identifiers

  • CVE-2026-41893
  • GHSA-vmfm-ch9h-5c7g

Timeline

  • 2026-04-05: other: Vulnerability reported via GHSA-vmfm-ch9h-5c7g
  • 2026-04-07: patched: Fix committed to master branch
  • 2026-04-19: advisory: Version 2.25.0 released with fix
  • 2026-05-09: disclosed: CVE-2026-41893 published

References

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