CVE-2026-45286: Nextcloud: Calendar app leaked user identifiers via attendee suggestion endpoint
Nextcloud is an open source content collaboration platform. From versions 5.5.13 to before 5.5.17, and 6.2.0 to before 6.2.3, an authenticated user can enumerate users on the same Nextcloud instance by using the Calendar app's endpoint for suggesting attendees. The sharing restrictions, applied to other endpoints, were not effective here. This issue has been patched in versions 5.5.17 and 6.2.3.
Affected Software
Remediation
Patch Available
Patch Available
Event History
Frequently Asked Questions
What is the severity of CVE-2026-45286?
CVE-2026-45286 has a medium severity rating of 4.3.
What does CVE-2026-45286 affect?
CVE-2026-45286 affects the Nextcloud Calendar app versions 5.5.13 to before 5.5.17 and 6.2.0 to before 6.2.3.
How does CVE-2026-45286 exploit user identifiers?
CVE-2026-45286 allows authenticated users to enumerate other users on the same Nextcloud instance through the attendee suggestion endpoint.
How do I fix CVE-2026-45286?
To fix CVE-2026-45286, you need to update your Nextcloud instance to versions 5.5.17 or later, or 6.2.3 or later.
What type of vulnerability is CVE-2026-45286 classified as?
CVE-2026-45286 is classified as an information leakage vulnerability.