CVE-2026-45281: Nextcloud Server

High severity, CVSS 8.1. EPSS: 0.5% chance of exploitation in the next 30 days.

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23

Affected products

• Nextcloud Nextcloud Server: from 32.0.0, before 32.0.9 (fixed in 32.0.9); from 33.0.0, before 33.0.3 (fixed in 33.0.3); from 21.0.0, before 21.0.9.23 (fixed in 21.0.9.23); from 22.0.0, before 22.2.10.39 (fixed in 22.2.10.39); from 23.0.0, before 23.0.12.35 (fixed in 23.0.12.35); from 24.0.0, before 24.0.12.34 (fixed in 24.0.12.34); …

Published 2026-06-01. Last modified 2026-07-22.