CVE-2026-45281 PUBLISHED

Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update

Assigner: GitHub_M
Reserved: 11.05.2026 Published: 01.06.2026 Updated: 01.06.2026

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

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CVSS Score: 8.1

Product Status

Vendor nextcloud
Product security-advisories
Versions
  • Version >= 32.0.0, < 32.0.9 is affected
  • Version >= 33.0.0, < 33.0.3 is affected

References

Problem Types

  • CWE-639: Authorization Bypass Through User-Controlled Key CWE