CVE-2026-39918 is a critical code injection vulnerability in givanz Vvveb prior to version 1.0.8.1. The issue occurs in the installation endpoint where the subdir POST parameter is unsafely written into the env.php configuration file without escaping or validation. This improper control of code generation (CWE-94) enables attackers to inject arbitrary PHP code by escaping the string context in the define statement, resulting in unauthenticated remote code execution with the privileges of the web server user. The vulnerability has a CVSS 4.0 score of 9.2, reflecting its critical impact and ease of exploitation. No official patch or remediation level is currently documented, and the product is not a cloud service, so remediation depends on vendor updates.

Successful exploitation allows unauthenticated remote attackers to execute arbitrary PHP code on the affected server with web server user privileges. This can lead to full compromise of the application environment, data exposure, and potential further attacks. The vulnerability is critical due to the lack of authentication required and the high impact of remote code execution.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to the installation endpoint to trusted users only and avoid exposing it publicly. Review and sanitize all inputs to the installation endpoint if possible. Monitor for vendor updates and apply patches promptly once released.