Vulnerability · Published Jul 31, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity unrestricted file upload in core from redaxo. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 56.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Packagist	redaxo/source	5.21.1	GHSA-98pp-vccm-qm25

Affected products (as reported)

Vendor	Product	Versions
redaxo	core	>= 5.18.2, < 5.21.1

Weakness: CWE-434 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/redaxo/core/security/advisories/GHSA-98pp-vccm-qm25 x_refsource_CONFIRM
https://github.com/redaxo/core/pull/6538 x_refsource_MISC
https://github.com/redaxo/core/commit/462e36896bb65d292ba22d711044c23c9cfb0340 x_refsource_MISC
https://github.com/redaxo/core/releases/tag/5.21.1 x_refsource_MISC