CVE-2025-66549: Nextcloud Desktop discloses information when attempting to lock a file inside a end-to-end encrypted directory

Severity: low (CVSS 2.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-05 · updated 2026-10-15
Weakness: CWE-209

Description

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.

Affected products

Desktop Client: from 3.0.0 before 3.16.5 — fixed in 3.16.5

How to fix

Upgrade to a fixed version: Desktop Client 3.16.5. Check the vendor advisory for mitigations.

References

https://github.com/nextcloud/desktop/commit/36d6c234d42b06a6f2e9de3e413a5c3c625edad6
https://github.com/nextcloud/desktop/pull/8330
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-h9xj-qh76-q3hw
https://hackerone.com/reports/3159877

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