CVE-2025-66547

Nextcloud Server users can modify tags on files that do not belong to them

CVSS 4.3 MEDIUMEPSS 0.2%CWE-639

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 4.3EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

05 Dec 2025Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected products

nextcloud · security-advisories

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References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hq6c-r898-fgf2 https://github.com/nextcloud/server/commit/b44f1568f2dc97c746281d99e2342ad679e3d8a9 https://github.com/nextcloud/server/issues/51247 https://github.com/nextcloud/server/pull/51288 https://hackerone.com/reports/3040887