CVE-2025-66549: Nextcloud Desktop is the desktop sync client for Nextcloud

Routine

LOW 2.4UPGRADE

CVE-2025-66549 is a low-severity flaw (CVSS 2.4) affecting desktop. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Nextcloud Desktop is the desktop sync client for Nextcloud. Prior to 3.16.5, when trying to manually lock a file inside an end-to-end encrypted directory, the path of the file was sent to the server unencrypted, making it possible for administrators to see it in log files. This vulnerability is fixed in 3.16.5.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	2.4 (Low)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-209
Published	2025-12-05
Last modified	2026-10-15

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

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-05 18:15 UTCPublished CVE record published
2026-10-15 21:10 UTCUpdated Record last modified

nextcloud desktop UPGRADE

Affected: >= 3.0.0 and < 3.16.5

Fixed in: 3.16.5

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy desktop || rpm -q desktop || desktop --version

2. UPGRADE to 3.16.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade desktop

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade desktop

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 3.0.0 (Debian / Ubuntu)

apt-cache madison desktop sudo apt install desktop=<VERSION_BEFORE_3.0.0> sudo apt-mark hold desktop

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

dnf --showduplicates list desktop sudo dnf downgrade desktop-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add desktop

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-2025-66549?

desktop: upgrade to 3.16.5. Exact commands for each OS are on this page.

Is CVE-2025-66549 being exploited?

CVE-2025-66549 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-2025-66549 affect?

CVE-2025-66549 affects desktop. Severity is low (CVSS 2.4). Nextcloud Desktop is the desktop sync client for Nextcloud. Prior to 3.16.5, when trying to manually lock a file inside an end-to-end encrypted directory, the path of the file was sent to the server unencrypted, making it possible for admin

How urgent is CVE-2025-66549?

Priority 14/100. No elevated risk signals yet.

Software pages

Nextcloud vulnerabilities

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References

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