Auth bypass in Nextcloud Server
CVE-2025-66547
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
EPSS: 0.002 (16.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
Affected products
- Nextcloud Nextcloud_server
- Nextcloud Security-advisories — versions < 31.0.1
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Permissions Required, x_refsource_MISC, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66547?
- CVE-2025-66547 is a medium-severity vulnerability in Nextcloud Server, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 4.3/10. Published 2025-12-05.
- How severe is CVE-2025-66547?
- Medium severity. CVSS v3 base score is 4.3 out of 10.