CVE-2025-66547: Nextcloud Server is a self hosted personal cloud system

Routine

MEDIUM 4.3UPGRADE

CVE-2025-66547 is a medium-severity flaw (CVSS 4.3) affecting nextcloud server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 80%)
CISA exploited list	No
Weakness	CWE-639
Published	2025-12-05
Last modified	2026-10-18

Publisher (CNA): GitHub, Inc. · Vendor: nextcloud

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-05 17:16 UTCPublished CVE record published
2026-10-18 14:10 UTCUpdated Record last modified

nextcloud nextcloud server UPGRADE

Affected: >= 31.0.0 and < 31.0.1

Fixed in: 31.0.1

Safe to downgrade to: a release before 31.0.0

1. Check installed version

apt-cache policy nextcloud-server || rpm -q nextcloud-server || nextcloud-server --version

2. UPGRADE to 31.0.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nextcloud-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nextcloud-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 31.0.0 (Debian / Ubuntu)

apt-cache madison nextcloud-server sudo apt install nextcloud-server=<VERSION_BEFORE_31.0.0> sudo apt-mark hold nextcloud-server

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nextcloud-server sudo dnf downgrade nextcloud-server-<VERSION_BEFORE_31.0.0> sudo dnf versionlock add nextcloud-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-66547?

nextcloud server: upgrade to 31.0.1. Exact commands for each OS are on this page.

Is CVE-2025-66547 being exploited?

CVE-2025-66547 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-66547 affect?

CVE-2025-66547 affects nextcloud server. Severity is medium (CVSS 4.3). 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 i

How urgent is CVE-2025-66547?

Priority 20/100. No elevated risk signals yet.

Software pages

Nextcloud vulnerabilities

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References

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