CVE-2025-47793 is a medium-severity vulnerability affecting multiple versions of Nextcloud Server, Nextcloud Enterprise Server, and the Nextcloud Groupfolders app. The vulnerability is classified under CWE-770, which pertains to the allocation of resources without limits or throttling. Specifically, in affected versions prior to Nextcloud Server 30.0.2, 29.0.9, and 28.0.1, as well as corresponding versions of the Enterprise Server and Groupfolders app, there is an absence of quota enforcement on attachments uploaded to group folders. This flaw allows authenticated users to upload files that exceed the configured group folder quota, effectively bypassing storage limits set by administrators. The vulnerability requires the user to be logged in but does not require user interaction beyond uploading files. The CVSS 3.1 base score is 4.3, indicating a medium severity level, with the vector AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N, meaning the attack can be performed remotely over the network with low attack complexity, requires privileges (logged-in user), no user interaction, unchanged scope, no confidentiality impact, limited integrity impact, and no availability impact. No known exploits are currently reported in the wild. The issue is fixed in Nextcloud Server versions 30.0.2, 29.0.9, 28.0.12, and Groupfolders app versions 18.0.3, 17.0.5, and 16.0.11. No workarounds are available, so patching is the primary remediation method. This vulnerability could lead to resource exhaustion or quota circumvention, potentially impacting storage management and administrative control over shared resources in collaborative environments.

For European organizations using Nextcloud for file sharing and collaboration, this vulnerability could allow authenticated users to bypass storage quotas on group folders, leading to uncontrolled resource consumption. This may result in storage exhaustion, degraded system performance, or denial of service for legitimate users due to quota overruns. While the vulnerability does not directly impact confidentiality or availability, the integrity of storage management policies is compromised, potentially causing operational disruptions. Organizations relying heavily on Nextcloud for regulated data or sensitive collaboration may face compliance risks if storage limits are not enforced, potentially violating data governance policies. Additionally, attackers or malicious insiders could exploit this flaw to disrupt workflows or consume disproportionate storage resources, impacting productivity and increasing administrative overhead. Given the widespread adoption of Nextcloud in European public and private sectors, especially in education, government, and enterprises emphasizing data sovereignty, the impact could be significant if unpatched.

The primary mitigation is to upgrade affected Nextcloud Server, Enterprise Server, and Groupfolders app installations to the fixed versions: Nextcloud Server 30.0.2 or later, 29.0.9 or later, 28.0.12 or later, and Groupfolders app 18.0.3 or later. Since no workarounds exist, organizations should prioritize patch management and schedule immediate updates. Additionally, administrators should audit group folder quotas and monitor storage usage patterns to detect abnormal increases that may indicate exploitation attempts. Implementing strict access controls to limit group folder upload permissions to trusted users can reduce risk exposure. Logging and alerting on quota violations or unusual upload activity can provide early detection. Organizations should also review their backup and recovery procedures to mitigate potential operational impacts from quota abuse. Finally, educating users about responsible resource usage and monitoring Nextcloud security advisories for further updates is recommended.