Executive Summary

CVE-2026-6257 is a remote code execution vulnerability in Vvveb CMS version 1.0.8 affecting its media management functionality.

The issue arises from a missing return statement in the file rename handler, which allows authenticated attackers to rename files to normally blocked extensions such as .php or .htaccess.

Attackers exploit this by first uploading a text file and renaming it to .htaccess, injecting Apache directives that register PHP-executable MIME types.

Then, they upload another file and rename it to .php, enabling execution of arbitrary operating system commands with the privileges of the www-data user.

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Impact Analysis

This vulnerability can lead to remote code execution on the affected server, allowing attackers to run arbitrary operating system commands.

Since the commands execute with the www-data user privileges, attackers could potentially manipulate website content, access sensitive data, or further compromise the server.

The high severity score (CVSS 9.1/9.2) reflects the critical impact of this flaw, including full confidentiality, integrity, and availability compromise.

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Detection Guidance

Detection of this vulnerability involves checking for unauthorized file renaming to blocked extensions such as .php or .htaccess within the media management functionality of Vvveb CMS.

You can monitor your web server or application logs for suspicious rename operations or uploads involving these extensions.

• Use commands to search for files with .php or .htaccess extensions in directories where uploads are stored, for example: `find /path/to/uploads -type f \( -name '*.php' -o -name '.htaccess' \)`
• Check web server access logs for requests that rename files or upload suspicious files.
• Audit the application logs or database entries related to media management rename operations for anomalies.

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Mitigation Strategies

Immediate mitigation involves applying the patch that fixes the rename handler to prevent renaming files to blocked extensions.

Specifically, ensure that the rename function enforces strict extension checks and returns an error when a disallowed extension is detected, as implemented in the official fix.

Until the patch is applied, restrict authenticated users' ability to rename files or upload files with dangerous extensions.

Additionally, monitor and block suspicious uploads or renames to .php or .htaccess files.

Consider restricting web server execution permissions in upload directories to limit the impact of any malicious files.

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Compliance Impact

The vulnerability allows authenticated attackers to execute arbitrary operating system commands on the server by exploiting a flaw in file renaming within the media management functionality. This can lead to unauthorized access, data breaches, and potential manipulation or exposure of sensitive information.

Such unauthorized access and potential data compromise can negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict controls to protect personal and sensitive data from unauthorized access and breaches.

Therefore, if exploited, this vulnerability could result in violations of these regulations due to failure to adequately secure systems against remote code execution and unauthorized data access.

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