CVE-2025-15009 is a vulnerability identified in liweiyi ChestnutCMS versions 1.5.0 through 1.5.8, specifically affecting the FilenameUtils.getExtension function used in the /dev-api/common/upload component. The flaw arises from improper handling and validation of the 'File' argument during upload operations, allowing attackers to bypass restrictions and perform unrestricted file uploads. This can lead to the placement of arbitrary files on the server, potentially enabling remote code execution, defacement, or further compromise depending on the server configuration and uploaded payload. The vulnerability is remotely exploitable without user interaction but requires low privileges, indicating that an attacker must have some level of access or be able to send crafted requests directly to the vulnerable endpoint. The CVSS 4.0 base score is 5.3, reflecting a medium severity with network attack vector, low complexity, no user interaction, and limited impact on confidentiality, integrity, and availability. Although no known exploits are currently active in the wild, proof-of-concept exploits have been published, increasing the risk of future attacks. The vulnerability stems from insufficient sanitization and validation of file extensions, which is critical in preventing malicious uploads. The lack of patch links suggests that official fixes may not yet be available, emphasizing the need for immediate mitigation steps by administrators.

For European organizations, this vulnerability poses a moderate risk primarily to web servers running vulnerable versions of ChestnutCMS. Successful exploitation could allow attackers to upload malicious scripts or executables, potentially leading to unauthorized access, data leakage, defacement, or disruption of services. Organizations handling sensitive data or providing critical services via ChestnutCMS are at risk of confidentiality breaches and integrity violations. The medium severity score indicates that while the impact is not catastrophic, it can still cause significant operational and reputational damage. Given the remote exploitability and lack of user interaction, attackers can automate attacks at scale, increasing exposure. The absence of known active exploits currently reduces immediate risk but the published proof-of-concept code lowers the barrier for attackers. European entities with web infrastructure using ChestnutCMS, especially those in sectors like government, finance, and healthcare, should consider this vulnerability a priority for remediation to avoid potential exploitation.

1. Immediately audit all instances of ChestnutCMS to identify affected versions (1.5.0 through 1.5.8). 2. If official patches become available, apply them without delay. 3. In the absence of patches, implement strict server-side validation to restrict file uploads by enforcing allowed file types and extensions explicitly. 4. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious upload attempts targeting the /dev-api/common/upload endpoint. 5. Restrict access to the upload API endpoint to authenticated and authorized users only, minimizing exposure. 6. Monitor logs for unusual upload activity or attempts to upload executable or script files. 7. Consider disabling or limiting file upload functionality if not essential. 8. Conduct regular security assessments and penetration testing focused on file upload mechanisms. 9. Educate development teams on secure coding practices related to file handling and input validation. 10. Maintain up-to-date backups and incident response plans to quickly recover from potential compromises.