CVE-2025-66547

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

MEDIUM
4.3
CVSS Score
Published: December 5, 2025 at 04:32 PM UTC
Updated: October 18, 2026 at 02:10 PM UTC
2 products affected across 1 vendorNextcloud/serversecurity-advisories

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Severity
MEDIUM4.3
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

31.0.0 ≤ v < 31.0.1

References (5)

x_refsource_MISCIssue Tracking
Source: cverecord
https://github.com/nextcloud/server/issues/51247
x_refsource_MISCIssue Tracking
Source: cverecord
https://github.com/nextcloud/server/pull/51288
x_refsource_MISCPermissions RequiredVendor Advisory
Source: cverecord
https://hackerone.com/reports/3040887

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.3MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-639

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