CVE-2026-23515

A Command Injection vulnerability allows authenticated users with write permissions to execute arbitrary shell commands on the Signal K server when the set-system-time plugin is enabled. Unauthenticated users can also exploit this vulnerability if security is disabled on the Signal K server. This occurs due to unsafe construction of shell commands when processing navigation.datetime values received via WebSocket delta messages.

Details

Product: Signal K set-system-time plugin
Repository: https://github.com/SignalK/set-system-time

File: index.js, lines 60-71

      stream.onValue(function (datetime) {
        var child
        if (process.platform == 'win32') {
          console.error("Set-system-time supports only linux-like os's")
        } else {
          if( ! plugin.useNetworkTime(options) ){
            const useSudo = typeof options.sudo === 'undefined' || options.sudo
            const setDate = `date --iso-8601 -u -s "${datetime}"`  // ← VULNERABLE
            const command = useSudo
              ? `if sudo -n date &> /dev/null ; then sudo ${setDate} ; else exit 3 ; fi`
              : setDate
            child = require('child_process').spawn('sh', ['-c', command])  // ← EXECUTES SHELL

The vulnerability has three components:

1. Unsanitized Input: The datetime value from navigation.datetime Signal K path is directly interpolated into a shell command without validation
2. Shell Execution: The command is executed via spawn('sh', ['-c', command]), which interprets shell metacharacters
3. Sudo Privileges: The plugin can execute with root privileges if sudo is misconfigured, instructions to limit passwordless sudo to the /bin/date binary helps mitigate this but RCE can still be achieved with the privileges of the user that installed it.

PoC

Exploitation Requirements

• Signal K server with security enabled, if disabled credentials not required
• Valid user credentials with readwrite or admin permissions
• set-system-time plugin installed and enabled
• Signal K server installed on a Linux OS
• Passwordless sudo configured, official instructions will do this for the date command which is enough to satisfy the if condition

"""
Run provided POC:
    python3 poc.py --host signalkserver_IP -u username -p password

Payload: Creates /tmp/signalk-RCE.txt to prove code execution
"""

Recommendations

• Replace shell-based execution with child_process.execFile() so user-controlled input is passed as arguments rather than interpreted by a shell.

• Validate that navigation.datetime conforms to an expected ISO-8601 format to improve robustness.

An attacker that has write privileges either through security on the Signal K server being disabled or valid credentials with read/write permissions can execute arbitrary commands on the server with the privileges of the SignalK process or root if sudo is misconfigured. This enables complete system compromise.

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-23515 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.5.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-23515? CVE-2026-23515 is a critical-severity OS command injection vulnerability in @signalk/set-system-time (npm), affecting versions < 1.5.0. It is fixed in 1.5.0. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
2. How severe is CVE-2026-23515? CVE-2026-23515 has a CVSS score of 9.9 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @signalk/set-system-time are affected by CVE-2026-23515? @signalk/set-system-time (npm) versions < 1.5.0 is affected.
4. Is there a fix for CVE-2026-23515? Yes. CVE-2026-23515 is fixed in 1.5.0. Upgrade to this version or later.
5. Is CVE-2026-23515 exploitable, and should I be worried? Whether CVE-2026-23515 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-23515 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-23515? Upgrade @signalk/set-system-time to 1.5.0 or later.