CVE-2026-53599: Redaxo Core

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

REDAXO is a PHP-based content management system. From 5.18.2 until 5.21.1, rex_mediapool::isAllowedExtension in redaxo/src/addons/mediapool/lib/mediapool.php lets an authenticated backend user with media[upload] permission upload a JPEG/PHP polyglot named shell.php.any.jpg, which web servers with multi-extension PHP handlers can execute as the web-server user. This issue is fixed in version 5.21.1.

Affected products

• Redaxo Core: from 5.18.2, before 5.21.1 (fixed in 5.21.1)

Published 2026-07-31. Last modified 2026-09-09.