Vvveb Unrestricted File Upload Vulnerability (CVE-2026-41937)

Vvveb is vulnerable to an unrestricted file upload vulnerability (CVE-2026-41937) affecting versions prior to 1.0.8.3. The vulnerability exists in the plugin upload endpoint, allowing super_admin users to upload arbitrary files. An attacker can exploit this by crafting a malicious plugin ZIP file containing a plugin.php file with a valid Slug header, alongside a public/index.php file containing arbitrary PHP code. Upon uploading this malicious plugin, the PHP code within public/index.php becomes accessible via unauthenticated HTTP requests to the plugin’s public path, resulting in remote code execution (RCE) as the web server user.

Attack Chain

1. An attacker identifies a Vvveb instance running a version prior to 1.0.8.3.
2. The attacker authenticates as a super_admin user.
3. The attacker crafts a malicious ZIP archive containing two files: plugin.php and public/index.php.
4. The plugin.php file includes a valid Slug header to bypass initial checks.
5. The public/index.php file contains arbitrary PHP code intended for execution.
6. The attacker uploads the crafted ZIP file through the plugin upload endpoint.
7. The Vvveb application extracts the ZIP file, placing the public/index.php in a publicly accessible directory.
8. The attacker sends an unauthenticated HTTP request to the public/index.php file’s URL, triggering the execution of the embedded PHP code on the server.

Impact

Successful exploitation of this vulnerability leads to arbitrary PHP code execution on the Vvveb server. This allows an attacker with super_admin privileges to gain complete control of the affected Vvveb instance, potentially leading to data breaches, defacement, or further lateral movement within the network. Due to the unrestricted nature of the file upload, attackers can deploy backdoors, execute system commands, and compromise the confidentiality, integrity, and availability of the application and underlying system.

Recommendation

• Upgrade Vvveb to version 1.0.8.3 or later to patch CVE-2026-41937.
• Implement the Sigma rule “Detect CVE-2026-41937 Exploitation Attempt — Vvveb Plugin Upload” to detect malicious plugin uploads based on HTTP request characteristics.
• Restrict access to the plugin upload endpoint to authorized personnel only.
• Monitor web server logs for suspicious activity, particularly requests to newly uploaded PHP files.