CVE-2025-9400 is a medium-severity vulnerability affecting YiFang CMS versions 2.0.0 through 2.0.5. The flaw exists in the mergeMultipartUpload function located in the file app/utils/base/plugin/P_file.php. Specifically, the vulnerability arises from improper handling and validation of the 'File' argument, which allows an attacker to perform unrestricted file uploads remotely without authentication or user interaction. This means an attacker can upload arbitrary files, potentially including malicious scripts or executables, to the server hosting the CMS. The vulnerability is exploitable over the network with low attack complexity and does not require privileges or user interaction, increasing its risk profile. Although the vendor was notified early, no response or patch has been issued, and while no known exploits are currently observed in the wild, proof-of-concept code has been published, raising the likelihood of future exploitation. The CVSS 4.0 base score is 5.3, reflecting medium severity, with the vector indicating network attack vector, low attack complexity, no privileges required, no user interaction, and limited impact on confidentiality, integrity, and availability. The unrestricted upload can lead to remote code execution, website defacement, data leakage, or further compromise depending on the uploaded payload and server configuration. The lack of vendor response and patch availability increases the urgency for organizations using YiFang CMS to implement mitigations.

For European organizations using YiFang CMS, this vulnerability poses a significant risk to web infrastructure security. Successful exploitation could allow attackers to upload malicious files, leading to remote code execution, unauthorized access, data breaches, or service disruption. This could compromise sensitive customer data, intellectual property, and operational continuity. Given the CMS's role in managing website content, attackers could deface websites, inject malware for supply chain attacks, or pivot to internal networks. The medium severity score suggests moderate but tangible risk, especially for organizations lacking compensating controls. The absence of vendor patches means organizations must rely on internal mitigations, increasing operational burden. Regulatory frameworks such as GDPR impose strict data protection requirements, and exploitation could lead to compliance violations and reputational damage. Additionally, the public availability of exploit code increases the likelihood of opportunistic attacks targeting European entities, especially those in sectors with high web presence such as e-commerce, media, and public services.

1. Immediate mitigation should include disabling or restricting the mergeMultipartUpload functionality if feasible, or applying web application firewall (WAF) rules to detect and block suspicious file upload requests targeting the vulnerable endpoint. 2. Implement strict input validation and file type restrictions at the application or server level to prevent unauthorized file types from being uploaded. 3. Employ network segmentation and least privilege principles to limit the impact of a potential compromise. 4. Monitor web server logs and application logs for unusual upload activity or access patterns indicative of exploitation attempts. 5. Use intrusion detection/prevention systems (IDS/IPS) with updated signatures to detect exploitation attempts. 6. If possible, isolate the CMS environment or deploy it in a sandboxed container to reduce risk. 7. Regularly back up website data and configurations to enable rapid recovery in case of compromise. 8. Engage with the vendor or community to track any forthcoming patches or updates and plan for timely application once available. 9. Educate IT and security teams about this vulnerability and the importance of monitoring for related indicators of compromise. 10. Consider alternative CMS platforms if the vendor remains unresponsive and the risk is unacceptable.