CVE-2026-76597 in Fabrik Extension
Summary
by MITRE • 08/22/2026
Joomla Extension - fabrikar.com - Unauthenticated arbitrary file upload to web root via list email plugin in Fabrik < 4.7.2 - The list email plugin controller allows to upload non-executable files to the webroot.
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Analysis
by VulDB Data Team • 08/22/2026
The vulnerability identified as a critical security flaw within Joomla extensions, specifically affecting versions of Fabrik prior to version 4.7.2, centers on an unauthenticated arbitrary file upload mechanism located in the list email plugin controller. This component is designed to facilitate communication between users and site administrators by allowing emails to be sent through forms generated by the extension. However, due to insufficient validation controls within the request handling logic of this specific module, attackers can exploit the interface to bypass authentication requirements entirely. The core technical flaw lies in the lack of rigorous checks on file types, extensions, and destination paths during the upload process initiated via the list email functionality. By crafting a malicious HTTP POST request that mimics legitimate form submissions but includes specially crafted payload files, an attacker can force the server to write these files directly into the web root directory where Joomla is installed.
From a technical perspective, this vulnerability represents a classic case of improper input validation leading to arbitrary file upload. The system fails to adequately sanitize or verify the nature of the uploaded content before committing it to disk. While the description notes that non-executable files are targeted, in many server configurations, particularly those running PHP with common web servers like Apache or Nginx, certain file extensions such as .php, .phtml, or even image formats with embedded script execution capabilities can be interpreted and executed by the server if placed within accessible directories. Even if the uploaded content is strictly non-executable in isolation, its presence in the web root allows for further exploitation vectors, including cross-site scripting (XSS) via stored payloads or directory traversal attacks that leverage the file's location to access sensitive configuration files like configuration.php which contain database credentials and other secrets.
The operational impact of this vulnerability is severe due to its unauthenticated nature. Attackers do not need valid user credentials, such as those for administrators or registered users, to initiate the exploit. This significantly lowers the barrier to entry for malicious actors, enabling automated scanning tools to target vulnerable instances across the internet with high efficiency. Once a file is successfully uploaded to the web root, it becomes publicly accessible via HTTP requests. If an executable script is uploaded and executed by the server, this results in remote code execution (RCE), granting the attacker full control over the underlying operating system or at least the context of the web server user. This can lead to complete site compromise, data exfiltration, defacement, or the use of the compromised server as a pivot point for further attacks against internal network resources.
This vulnerability aligns with CWE-434, which describes the unrestricted upload of files with dangerous types, and CWE-20, indicating improper input validation. In terms of attack taxonomy, it maps to MITRE ATT&CK technique T1505.003, known as Web Shell: Cloud Services or general web shell deployment via file upload mechanisms. The exploitation path typically involves crafting a multipart form data request that includes the malicious payload alongside standard form fields expected by the list email plugin, thereby bypassing basic security filters that might check for authentication tokens if they are not strictly enforced on this specific endpoint.
Mitigation strategies must prioritize immediate patching of the Fabrik extension to version 4.7.2 or later, where these validation checks have been corrected. In environments where updating is not immediately feasible, administrators should implement web application firewall (WAF) rules that detect and block suspicious file upload patterns targeting the specific controller endpoints associated with the list email plugin. Additionally, restricting write permissions on the Joomla installation directories to prevent arbitrary writes from the web server process can serve as a defensive layering measure. Regular auditing of uploaded files in public-facing directories is also recommended to ensure no unauthorized content has been persisted by previous exploitation attempts.