CVE-2023-53956: Altervista Flatnux

High severity, CVSS 8.8. EPSS: 0.8% chance of exploitation in the next 30 days.

Flatnux 2021-03.25 contains an authenticated file upload vulnerability that allows administrative users to upload arbitrary PHP files through the file manager. Attackers with admin credentials can upload malicious PHP scripts to the web root directory, enabling remote code execution on the server.

Affected products

• Altervista Flatnux: version 2021-03.25 only

Published 2025-12-19. Last modified 2026-06-17.