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
EPSS: 0.003 (20.2th percentile) — read the EPSS interpretation.
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.
Affected products
- Nextcloud Calendar
- Nextcloud Security-advisories — versions >= 5.5.13, < 5.5.17, >= 6.2.0, < 6.2.3
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
- security-advisories@github.com (Exploit, Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Permissions Required, x_refsource_MISC)
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.