CVE-2025-34100 is a critical security vulnerability identified in BuilderEngine CMS version 3.5.0. The root cause stems from the integration of the elFinder 2.0 file manager, which utilizes the jQuery File Upload plugin. This plugin fails to adequately validate or restrict file types and upload locations, permitting attackers to upload malicious files, specifically .php scripts. Due to BuilderEngine's improper integration and lack of access control mechanisms, this file upload functionality is exposed to unauthenticated users. Consequently, an attacker can upload a crafted PHP file and execute arbitrary code on the server with the privileges of the web server process. This results in full remote code execution (RCE) without requiring authentication or user interaction. The vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type), CWE-20 (Improper Input Validation), and CWE-306 (Missing Authentication for Critical Function). The CVSS 4.0 base score is 9.3 (critical), reflecting the ease of exploitation (network attack vector, no privileges or user interaction required) and the high impact on confidentiality, integrity, and availability. Although the underlying issue originates from the jQuery File Upload component, BuilderEngine's failure to implement proper access controls and input validation significantly amplifies the risk. No patches or fixes are currently linked, and no known exploits have been reported in the wild as of the publication date (July 10, 2025).

For European organizations using BuilderEngine CMS 3.5.0, this vulnerability poses a severe risk. Successful exploitation allows attackers to execute arbitrary PHP code remotely, potentially leading to full system compromise. This can result in data breaches, defacement, deployment of ransomware, or use of the compromised server as a pivot point for lateral movement within internal networks. Confidentiality is at high risk due to unauthorized data access; integrity is compromised through unauthorized code execution and potential data manipulation; availability can be disrupted by denial-of-service conditions or destructive payloads. Given the unauthenticated nature of the exploit, attackers can scan for vulnerable BuilderEngine instances and compromise them en masse. This is particularly concerning for European organizations handling sensitive personal data under GDPR, as breaches could lead to regulatory penalties and reputational damage. Additionally, the lack of user interaction and authentication requirements makes automated exploitation feasible, increasing the threat surface.

European organizations should immediately audit their web infrastructure to identify any BuilderEngine CMS 3.5.0 deployments. In the absence of an official patch, mitigation should focus on restricting access to the vulnerable file upload functionality. This can be achieved by implementing strict network-level access controls such as IP whitelisting or VPN-only access to the CMS administration interfaces. Web application firewalls (WAFs) should be configured to detect and block attempts to upload .php or other executable files, and to monitor for suspicious file upload patterns. Additionally, disabling or removing the elFinder file manager or the jQuery File Upload plugin until a secure patch is available is advisable. Organizations should also implement strict input validation and file type restrictions at the application level, ensuring only safe file types are accepted. Regular monitoring of server logs for unusual upload activity and deploying intrusion detection systems can help detect exploitation attempts. Finally, organizations should prepare incident response plans tailored to web server compromises and consider isolating affected systems to prevent lateral movement.