Information disclosure in Nextcloud Calendar
CVE-2026-45286
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.
Vulnerability class: Information Disclosure
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (38.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Nextcloud Calendar
- Nextcloud Security-Advisories — versions >= 5.5.13, < 5.5.17, >= 6.2.0, < 6.2.3
Weakness classification (CWE)
References
- github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 (Mitigation, Vendor Advisory)
- github.com/nextcloud/calendar/issues/7971 (Exploit, Patch, Issue Tracking)
- github.com/nextcloud/calendar/pull/8197 (Patch, Issue Tracking)
- hackerone.com/reports/3540663 (Permissions Required)
Frequently asked questions
- What is CVE-2026-45286?
- CVE-2026-45286 is a medium-severity vulnerability in Nextcloud Calendar, classified under Information Disclosure. CVSS score: 4.3/10. Published 2026-06-01.
- How severe is CVE-2026-45286?
- Medium severity. CVSS v3 base score is 4.3 out of 10.