CVE-2025-66547: Nextcloud Server <31.0.1 Bulk Tagging A/C Bypass
CVE-2025-66547 Published on December 5, 2025
Nextcloud Server users can modify tags on files that do not belong to them
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 Analysis
CVE-2025-66547 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is an Insecure Direct Object Reference / IDOR Vulnerability?
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
CVE-2025-66547 has been classified to as an Insecure Direct Object Reference / IDOR vulnerability or weakness.
Products Associated with CVE-2025-66547
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Affected Versions
nextcloud security-advisories Version < 31.0.1 is affected by CVE-2025-66547Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.