4.3Medium
CVE-2026-45286Nextcloud: Calendar app leaked user identifiers via attendee suggestion endpoint
Description
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.
Weakness (CWE):
CWE-200
Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.
Affected products and versions
| Vendor | Product | Versions | |
|---|---|---|---|
| nextcloud | calendar | 5.5.13 – < 5.5.17 | |
| nextcloud | security-advisories | >= 5.5.13, < 5.5.17, >= 6.2.0, < 6.2.3 |
References and patches
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 MitigationVendor Advisory
- https://github.com/nextcloud/calendar/issues/7971 ExploitIssue TrackingPatch
- https://github.com/nextcloud/calendar/pull/8197 Issue TrackingPatch
- https://hackerone.com/reports/3540663
CPE matches (NVD) (2)
cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*≥ 5.5.13 < 5.5.17cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*≥ 6.2.0 < 6.2.3