CVE-2025-6776 is a path traversal vulnerability identified in the openvpn-cms-flask product developed by xiaoyunjie, affecting versions 1.2.0 through 1.2.7. The vulnerability resides in the file upload functionality, specifically within the Upload function located in app/plugins/oss/app/controller.py. An attacker can manipulate the 'image' argument during file upload to perform a path traversal attack, allowing unauthorized access to files and directories outside the intended upload directory. This can lead to exposure or modification of sensitive files on the server. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS 4.0 base score is 6.9, categorized as medium severity, reflecting the network attack vector, low complexity, and no privileges or user interaction needed. The vulnerability affects confidentiality, integrity, and availability to a limited extent due to the potential for unauthorized file access or overwriting critical files. A patch addressing this issue was released in version 1.2.8, with the fix identified by commit e23559b98c8ea2957f09978c29f4e512ba789eb6. Although no known exploits are currently observed in the wild, the public disclosure and ease of exploitation make it a credible threat. Organizations using openvpn-cms-flask versions prior to 1.2.8 should prioritize upgrading to mitigate this vulnerability.

For European organizations, the impact of CVE-2025-6776 can be significant depending on the deployment scale of openvpn-cms-flask. As this product is related to OpenVPN management via a Flask-based CMS, it is likely used in network infrastructure or VPN management contexts. Exploitation could allow attackers to access or modify sensitive configuration files, credentials, or other critical data stored on the server, potentially leading to unauthorized network access or disruption of VPN services. This could compromise confidentiality of internal communications and integrity of VPN configurations. Availability impact is possible if critical files are overwritten or deleted. Given the remote, unauthenticated exploit vector, attackers could leverage this vulnerability to gain footholds in corporate networks, especially in sectors relying heavily on VPNs for secure remote access, such as finance, healthcare, and government institutions in Europe. The medium CVSS score suggests moderate but non-trivial risk, emphasizing the need for timely patching to prevent lateral movement or data breaches.

European organizations should immediately upgrade openvpn-cms-flask to version 1.2.8 or later to apply the official patch. In addition to patching, organizations should implement strict input validation and sanitization on file upload parameters to prevent path traversal attempts. Deploying web application firewalls (WAFs) with rules tuned to detect and block path traversal payloads targeting the 'image' parameter can provide an additional layer of defense. Regularly audit and monitor file system access logs for unusual file access patterns or unauthorized file modifications. Restrict file system permissions for the application user to the minimum necessary, preventing access to sensitive directories outside the upload folder. Network segmentation should isolate VPN management interfaces from general user networks to limit exposure. Finally, conduct vulnerability scanning and penetration testing focused on file upload functionalities to proactively identify similar weaknesses.