CVE-2025-3566 is a vulnerability identified in version 4.2 of the veal98 小牛肉 Echo 开源社区系统, an open-source community system platform. The vulnerability exists in the uploadMdPic function located at the /discuss/uploadMdPic endpoint. Specifically, the issue arises from improper handling of the 'editormd-image-file' argument, which allows an attacker to perform unrestricted file uploads. This means that an attacker can remotely upload arbitrary files without authentication or user interaction, potentially leading to the execution of malicious code or the placement of harmful files on the server. The vulnerability has been publicly disclosed, increasing the risk of exploitation, although no known exploits have been observed in the wild yet. The CVSS 4.0 base score is 6.9, indicating a medium severity level. The vector details show that the attack can be performed remotely (AV:N), requires no privileges (PR:N), no user interaction (UI:N), and has low impact on confidentiality, integrity, and availability (VC:L, VI:L, VA:L). The scope remains unchanged (S:N), and there are no known patches currently available. The unrestricted upload flaw is critical because it can be leveraged to upload web shells or other malicious payloads, potentially leading to full system compromise if the server executes or serves these files. However, the medium CVSS score reflects the limited impact due to the low confidentiality, integrity, and availability impacts as assessed, possibly because of mitigations or environment-specific factors.

For European organizations using the veal98 Echo 开源社区系统 version 4.2, this vulnerability poses a significant risk. Unrestricted file upload vulnerabilities are commonly exploited to gain initial access or escalate privileges within a network. Attackers could upload web shells or malware, leading to data breaches, defacement, or lateral movement within the network. Given the public disclosure and absence of patches, organizations face increased exposure. The impact on confidentiality is moderate since attackers could access sensitive data through uploaded malicious files. Integrity and availability impacts are also moderate, as attackers might alter or disrupt services by uploading harmful content. European organizations relying on this platform for community engagement or internal collaboration could experience reputational damage, regulatory penalties under GDPR if personal data is compromised, and operational disruptions. The risk is heightened for organizations with internet-facing instances of the affected software without adequate compensating controls.

Immediate mitigation should focus on restricting access to the /discuss/uploadMdPic endpoint via network controls such as web application firewalls (WAFs) configured to block suspicious file uploads or limit upload types and sizes. Organizations should implement strict input validation and file type verification at the application or proxy level to prevent unauthorized file types from being uploaded. Deploying runtime application self-protection (RASP) or endpoint detection and response (EDR) tools can help detect and block exploitation attempts. Until an official patch is released, consider disabling the uploadMdPic functionality if feasible or restricting it to authenticated and authorized users only. Regularly monitor server logs for unusual upload activity and conduct thorough security assessments of the affected systems. Additionally, isolate the affected system from critical internal networks to limit potential lateral movement. Organizations should also prepare for rapid patch deployment once a fix becomes available and maintain up-to-date backups to enable recovery from potential compromises.