Auth bypass in Nextcloud Server
CVE-2026-45283
Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.2, and 33.0.0 to before 33.0.1, the files_lock app did not properly validate the ownership of files when processing DAV lock and unlock requests. An authenticated user could lock or unlock files belonging to other users by targeting their absolute WebDAV paths. Additionally, lock tokens were disclosed to unauthorized callers in error responses, allowing attackers to remove token-based locks placed by other users' client applications. It is recommended that the Nextcloud Server is upgraded to 32.0.2 or 33.0.1. It is recommended that the Nextcloud Enterprise Server is upgraded to 31.0.14.4 or 32.0.2 or 33.0.1
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L.
EPSS exploit prediction
EPSS: 0.004 (27.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 27.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
- Nextcloud Server
- Nextcloud Security-Advisories — versions >= 32.0.0, < 32.0.2, >= 33.0.0, < 33.0.1
Weakness classification (CWE)
References
- github.com/nextcloud/security-advisories/security/advisories/GHSA-4chh-6mhf-p4jj (Vendor Advisory)
- github.com/nextcloud/files_lock/pull/1007 (Patch, Issue Tracking)
- hackerone.com/reports/3301553 (Permissions Required)
Frequently asked questions
- What is CVE-2026-45283?
- CVE-2026-45283 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Authentication. CVSS score: 6.3/10. Published 2026-06-01.
- How severe is CVE-2026-45283?
- Medium severity. CVSS v3 base score is 6.3 out of 10.