CVE-2025-66547: Nextcloud Server

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Nextcloud Server is a self hosted personal cloud system. In Nextcloud Server and Enterprise Server prior to 31.0.1, non-privileged users can modify tags on files they should not have access to via bulk tagging. This vulnerability is fixed in 31.0.1.

Affected products

• Nextcloud Nextcloud Server: from 31.0.0, before 31.0.1 (fixed in 31.0.1)

Published 2025-12-05. Last modified 2026-06-17.