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 the risk of exploitation. Although the vendor was notified early, no response or patch has been provided, and a public exploit has been published, increasing the likelihood of active exploitation in the wild. The CVSS 4.0 base score is 5.3, reflecting medium severity with partial impact on confidentiality, integrity, and availability. The vulnerability does not require authentication, which broadens the attack surface. Exploitation could lead to remote code execution, website defacement, data theft, or use of the compromised server as a pivot point for further attacks. The lack of vendor response and patch availability heightens the urgency for organizations using YiFang CMS to implement mitigations or consider alternative CMS solutions.

For European organizations using YiFang CMS, this vulnerability poses a significant risk to web infrastructure security. Successful exploitation could lead to unauthorized access, data breaches involving sensitive customer or business data, defacement of public-facing websites, and disruption of services. This could damage organizational reputation, lead to regulatory non-compliance (e.g., GDPR violations), and result in financial losses. Given the unrestricted upload capability, attackers could deploy web shells or malware, facilitating persistent access and lateral movement within corporate networks. The medium severity rating suggests moderate but tangible risk, especially for organizations lacking compensating controls such as web application firewalls or strict network segmentation. The absence of vendor patches means European entities must rely on internal security measures to mitigate risk. Industries with high reliance on web presence, such as e-commerce, media, and public sector services, are particularly vulnerable. Additionally, the public availability of exploits increases the likelihood of opportunistic attacks targeting European organizations.

1. Immediate mitigation should involve restricting access to the vulnerable upload functionality through network-level controls such as IP whitelisting or VPN-only access. 2. Deploy web application firewalls (WAFs) with custom rules to detect and block suspicious multipart upload requests or anomalous file types. 3. Implement strict server-side validation and sanitization of uploaded files, including limiting allowed file extensions and scanning uploads with antivirus and malware detection tools. 4. Monitor web server logs for unusual upload activity or access patterns indicative of exploitation attempts. 5. If possible, disable or remove the mergeMultipartUpload function or the entire plugin until a vendor patch is available. 6. Conduct regular security audits and penetration tests focusing on file upload mechanisms. 7. Consider migrating to alternative CMS platforms with active vendor support and timely patching. 8. Maintain up-to-date backups of web content and configurations to enable rapid recovery in case of compromise. 9. Educate IT and security teams about this vulnerability and the importance of monitoring for exploitation attempts. 10. Engage with the vendor or community to track any forthcoming patches or advisories.