Vvveb Unrestricted File Upload Leads to Remote Code Execution (CVE-2026-41938)

Vvveb, a content management system, is vulnerable to an unrestricted file upload vulnerability (CVE-2026-41938) in versions prior to 1.0.8.2. This flaw allows authenticated users with the necessary media upload permissions to circumvent existing extension restrictions. By uploading a specially crafted .htaccess file, an attacker can map the .phtml extension to the PHP handler. Subsequently, they can upload a .phtml file containing malicious PHP code. The vulnerability is triggered when an unauthenticated HTTP GET request is sent to the uploaded .phtml file, leading to remote code execution on the web server. This poses a significant risk to organizations using vulnerable versions of Vvveb, potentially enabling complete system compromise.

Attack Chain

1. An attacker authenticates to the Vvveb application with media upload permissions.
2. The attacker uploads a .htaccess file. This file configures the webserver to interpret files with the .phtml extension as PHP code. For example, the .htaccess file might contain the line AddType application/x-httpd-php .phtml.
3. The attacker uploads a .phtml file containing malicious PHP code. For example, the file might contain <?php system($_GET['cmd']); ?>.
4. The Vvveb application stores the uploaded .htaccess and .phtml files in the media directory.
5. The attacker sends an unauthenticated HTTP GET request to the uploaded .phtml file, including a command to execute as a parameter, such as http://example.com/media/evil.phtml?cmd=whoami.
6. The web server, due to the .htaccess configuration, interprets the .phtml file as PHP code.
7. The PHP interpreter executes the command specified in the HTTP GET request (whoami in this example).
8. The attacker gains remote code execution on the server with the privileges of the web server user.

Impact

Successful exploitation of CVE-2026-41938 allows an attacker to execute arbitrary code on the Vvveb server. This can lead to complete compromise of the server, including data theft, modification, or destruction. Given a CVSS v3.1 base score of 8.8, this vulnerability poses a critical risk. The scope of impact depends on the permissions of the web server user, but it could extend to other systems on the network. There is no information about observed exploitation or specific victims.

Recommendation

• Upgrade Vvveb to version 1.0.8.2 or later to patch CVE-2026-41938.
• Implement the Sigma rule “Detect Vvveb .htaccess Upload” to identify attempts to upload malicious .htaccess files.
• Deploy the Sigma rule “Detect Vvveb PHTML File Execution” to detect execution of .phtml files within the Vvveb media directory.
• Review web server access logs for suspicious requests to .phtml files, as detected by the “Detect Vvveb PHTML File Execution” rule, especially those containing command execution parameters.