CVE-2021-28428: Horizontcms Project Horizontcms

Critical severity, CVSS 9.8. EPSS: 1.2% chance of exploitation in the next 30 days.

File upload vulnerability in HorizontCMS before 1.0.0-beta.3 via uploading a .htaccess and *.hello files using the Media Files upload functionality. The original file upload vulnerability (CVE-2020-27387) was remediated by restricting the PHP extensions; however, we confirmed that the filter was bypassed via uploading an arbitrary .htaccess and *.hello files in order to execute PHP code to gain RCE.

Affected products

• Horizontcms Project Horizontcms: version 1.0.0 only

Published 2022-04-05. Last modified 2026-06-17.