CVE-2026-25228
📋 TL;DR
Signal K Server versions prior to 2.20.3 on Windows systems contain a path traversal vulnerability in the applicationData API. Authenticated users can exploit this to read, write, and list arbitrary files and directories on the filesystem by using backslashes (\\) to bypass validation. This affects boat operators and administrators running vulnerable versions on Windows.
💻 Affected Systems
- Signal K Server
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could read sensitive system files (e.g., configuration, credentials), write malicious files to execute code, or delete critical data, potentially compromising the entire boat's control system.
Likely Case
An authenticated user with malicious intent could access or modify application data, configuration files, or other sensitive information stored on the server, leading to data breaches or system disruption.
If Mitigated
With proper access controls and monitoring, exploitation might be limited to non-critical files or detected early, minimizing damage.
🎯 Exploit Status
Exploitation requires authenticated access; the vulnerability is straightforward to exploit on Windows due to the validation bypass.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.20.3
Vendor Advisory: https://github.com/SignalK/signalk-server/security/advisories/GHSA-vrhw-v2hw-jffx
Restart Required: Yes
Instructions:
1. Backup your Signal K Server configuration and data. 2. Update to version 2.20.3 or later using your package manager or by downloading from the official repository. 3. Restart the Signal K Server service to apply the patch.
🔧 Temporary Workarounds
Restrict Access to ApplicationData API
allLimit network access to the Signal K Server API to trusted users only, reducing the attack surface.
Configure firewall rules to block external access to the Signal K Server port (e.g., 3000 by default).
Monitor for Suspicious File Operations
windowsImplement file system monitoring to detect unauthorized access attempts via the applicationData API.
Use tools like Windows Event Log or third-party monitoring solutions to track file read/write operations in the Signal K Server directories.
🧯 If You Can't Patch
- Migrate the Signal K Server to a Linux or macOS system, as the vulnerability is specific to Windows.
- Implement strict authentication and authorization controls to limit which users can access the applicationData API.
🔍 How to Verify
Check if Vulnerable:
Check the Signal K Server version; if it is below 2.20.3 and running on Windows, it is vulnerable.Check Version:
Run `signalk-server --version` or check the server logs for version information.Verify Fix Applied:
After updating, confirm the version is 2.20.3 or higher and test that backslash inputs in the applicationData API are properly blocked.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in applicationData API logs, such as requests containing backslashes (\\) or attempts to access paths outside the intended directory.
Network Indicators:
- HTTP requests to the applicationData endpoint with suspicious parameters, especially from untrusted IP addresses.
SIEM Query:
Example: `source="signalk-server.log" AND (message="*applicationData*" AND message="*\\*" )`