CVE-2026-53599 Redaxo has a Mediapool isAllowedExtension bypass via multi-segment filename that leads to authenticated RCE on Apache mod_php multi-extension handlers

REDAXO is a PHP-based content management system. From 5.18.2 until 5.21.1, rexmediapool::isAllowedExtension in redaxo/src/addons/mediapool/lib/mediapool.php lets an authenticated backend user with mediaupload permission upload a JPEG/PHP polyglot named shell.php.any.jpg, which web servers with...

CVE-2026-53599

CVE-2026-53599 affects REDAXO CMS versions 5.18.2–5.21.1 where rex_mediapool::isAllowedExtension lets an authenticated backend user with media[upload] permission upload a JPEG/PHP polyglot named shell.php.any.jpg. On servers with multi-extension PHP handlers, this can be executed as the web serve...