The vulnerability identified as CVE-2025-65963 affects the cfiles module of HumHub, a social collaboration platform widely used for managing files within user profiles and spaces. Specifically, this flaw arises from improper access control (CWE-284) where authorization checks are insufficient in public spaces, allowing non-member users to create new folders and upload or download files as ZIP archives. This means that users without membership privileges can manipulate files in public spaces, potentially leading to unauthorized data exposure or tampering. Private spaces are not impacted by this vulnerability, indicating that the access control issue is scoped to public collaboration areas. The affected versions are all releases before 0.16.11 and between 0.17.0 and 0.17.2, with patches released in 0.16.11 and 0.17.2 to address the issue. The CVSS v3.1 score is 5.4 (medium severity), reflecting a network attack vector, low attack complexity, and requiring low privileges but no user interaction. The vulnerability impacts confidentiality and integrity but does not affect availability. No known exploits have been reported in the wild, but the potential for unauthorized data access or modification exists if exploited. This vulnerability is particularly relevant for organizations using HumHub for public collaboration spaces, where sensitive or regulated data might be exposed or altered by unauthorized users.

For European organizations, this vulnerability poses a risk of unauthorized data access and manipulation within public collaboration spaces on HumHub platforms. Confidential information stored or shared in these public spaces could be exposed or altered by non-members, potentially leading to data breaches or compliance violations under regulations such as GDPR. Although private spaces remain secure, organizations relying heavily on public spaces for file sharing and collaboration could face reputational damage and operational disruption. The integrity of shared documents could be compromised, affecting business processes and trust among collaborators. Since the vulnerability does not impact availability, denial-of-service is less of a concern. However, the ease of exploitation due to low attack complexity and network accessibility means that attackers could automate exploitation attempts, increasing risk. European entities in sectors with strict data protection requirements, such as finance, healthcare, and government, may be particularly sensitive to such unauthorized access and data integrity issues.

Organizations should immediately upgrade HumHub cfiles to versions 0.16.11 or 0.17.2 or later to apply the official patches. Until patching is complete, administrators should review and restrict permissions on public spaces to limit file management capabilities to trusted users only. Implement network-level access controls to limit exposure of HumHub instances to trusted networks or VPNs. Conduct audits of public space contents to detect unauthorized files or folders created by non-members. Enable detailed logging and monitoring of file operations within public spaces to detect anomalous activities. Educate users and administrators about the risks of using public spaces for sensitive data. Consider disabling or limiting the use of the cfiles module in public spaces if patching is delayed. Regularly review HumHub security advisories for updates or additional mitigations. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious file upload or creation attempts targeting this vulnerability.