Arbitrary file upload in Redaxo Core

CVE-2026-53599

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.

Vulnerability class: Unrestricted File Upload

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (43.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-53599: held from 0.005 to 0.005.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-53599?
CVE-2026-53599 is a high-severity vulnerability in Redaxo Core, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 7.5/10. Published 2026-07-31.
How severe is CVE-2026-53599?
High severity. CVSS v3 base score is 7.5 out of 10.