CVE-2026-42238: Nginx-UI is Vulnerable to Unauthenticated Remote Code Execution via Backup Restore

nginx-ui exposes a backup restore endpoint (POST /api/restore) that is completely unauthenticated during the first 10 minutes after process startup on any fresh installation. An unauthenticated remote attacker can upload a crafted backup archive that overwrites the application’s configuration file (app.ini) and SQLite database. Because the attacker controls the restored app.ini, they can inject an arbitrary OS command into the TestConfigCmd setting. After the application automatically restarts to apply the restored config, a single follow-up request triggers that command as the user running nginx-ui — typically root in Docker deployments.

The 10-minute unauthenticated window resets on every process restart, making this exploitable not only on initial deployments but on any restart event (container restart, upgrade, health-check-triggered restart).