Vvveb CMS 1.0.8 Remote Code Execution via Malicious Upload

Vvveb CMS version 1.0.8 is susceptible to a remote code execution (RCE) vulnerability (CVE-2026-6249) due to insufficient input validation in the media upload handler. An authenticated attacker can exploit this flaw by uploading a malicious PHP webshell disguised with a .phtml extension, which bypasses the server’s intended extension deny-list. The uploaded webshell is then accessible within the publicly available media directory. By crafting a specific HTTP request to access the uploaded .phtml file, the attacker can trigger the execution of arbitrary operating system commands on the server, leading to a complete compromise of the system. This vulnerability poses a significant threat to organizations utilizing Vvveb CMS 1.0.8, potentially enabling attackers to steal sensitive data, disrupt services, or establish a persistent foothold within the network.

Attack Chain

1. The attacker authenticates to the Vvveb CMS 1.0.8 instance.
2. The attacker accesses the media upload functionality within the CMS.
3. The attacker uploads a malicious PHP webshell file, named with a .phtml extension, crafted to execute operating system commands.
4. The CMS stores the uploaded .phtml file in the publicly accessible media directory.
5. The attacker crafts an HTTP request targeting the uploaded .phtml file in the media directory.
6. The web server executes the PHP code within the .phtml file upon receiving the attacker’s HTTP request.
7. The PHP code executes arbitrary operating system commands, as defined by the attacker in the webshell.
8. The attacker gains complete control of the server, potentially leading to data theft, service disruption, or persistent access.

Impact

Successful exploitation of CVE-2026-6249 allows an attacker to execute arbitrary operating system commands on the Vvveb CMS server. This could lead to a full compromise of the system, including the theft of sensitive data stored in the CMS database, modification of website content, or the deployment of malicious software. Organizations using Vvveb CMS 1.0.8 are at risk of data breaches, financial losses, and reputational damage if this vulnerability is exploited.

Recommendation

• Upgrade Vvveb CMS to a patched version that addresses CVE-2026-6249.
• Implement strict input validation and sanitization on all file upload functionalities to prevent the upload of malicious files.
• Configure the web server to prevent the execution of PHP code within the media directory.
• Deploy the Sigma rule Detect Suspicious PHTML Request to identify attempts to access .phtml files in the media directory.
• Monitor web server logs for suspicious HTTP requests targeting unusual file extensions in media directories.