Vulnerable File Upload in Vvveb CMS Enables RCE

Executive Summary

CVE-2026-126378 is a critical file upload vulnerability in Vvveb CMS versions 1.0.8.6 and earlier. The theme installer's validFile() function uses strpos() for path validation, which checks if /theme.php exists anywhere in the path instead of at the end. This allows attackers with admin access to upload a malicious ZIP containing a PHP file with a path like mytheme/scripts/theme.php, bypassing restrictions and achieving remote code execution on nginx deployments.

The flaw stems from weak path matching logic and the absence of PHP execution restrictions in nginx's default configuration for the /themes/ directory. Apache deployments are protected by .htaccess, but nginx users are fully exposed.

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Detection Guidance

Check for unauthorized PHP files in the themes directory, particularly those with paths containing 'theme.php' anywhere in the filename. Inspect nginx access logs for suspicious uploads or file extractions to /public/themes/. Use commands like 'find /path/to/themes -name "*.php"' to locate PHP files in theme directories.

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Impact Analysis

If exploited, this vulnerability allows attackers with admin credentials to execute arbitrary PHP code on the server, leading to full system compromise. This includes reading sensitive files (like database credentials), executing system commands, escalating privileges, or maintaining persistent access. The impact is severe as it grants control over the entire server.

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Compliance Impact

This vulnerability likely violates compliance requirements for GDPR and HIPAA due to unauthorized access to sensitive data. GDPR mandates strict data protection and breach notification, while HIPAA requires safeguards for protected health information. A successful exploit could lead to unauthorized data exposure, triggering regulatory penalties and legal consequences.

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Mitigation Strategies

Upgrade Vvveb to a patched version if available. Modify the validFile() function to reject all PHP files unconditionally. Add a deny rule in nginx configuration to block PHP execution in the /themes/ directory. Remove any unauthorized PHP files from the themes directory immediately.

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