CVE-2026-56290

The vulnerability results from insufficient access control (CWE-284) in the file upload mechanism of the Page Builder CK extension. An attacker without any authentication can send an HTTP request containing an executable file (e.g., PHP webshell) to the vulnerable endpoint. After successful upload, the file is saved in a location accessible by the web server, enabling its remote invocation and execution of arbitrary system commands.

The attacker gains full control over the server — can execute arbitrary system commands, read and modify data, and use the compromised server as a launching point for further attacks on the internal network.

Apply patches available from the vendor according to the references (https://www.joomlack.fr/). Until the update is implemented, it is recommended to disable or uninstall the Page Builder CK extension and restrict access to the Joomla service at the firewall level.

Page Builder CK extension for Joomla — versions indicated in the vendor references (https://www.joomlack.fr/)

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Joomlack Page Builder contains an improper access control vulnerability that could allow for remote code execution via unauthenticated arbitrary file upload.