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Vulnerability record · CVE-2026-45286 · published 1 June 2026

CVE-2026-45286: Nextcloud calendar information exposure vulnerability

Nextcloud · Calendar

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.

4.3 CVSS 3.1 Medium EPSS 0.46% · top 62.9% CWE-200 · Information exposure
4.3CVSS 3.1 base score
0.46%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 1 tagged exploit
22 Jul 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/nextcloud/calendar/issues/7971 ExploitIssue TrackingPatch
https://github.com/nextcloud/calendar/pull/8197 Issue TrackingPatch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 MitigationVendor Advisory
https://hackerone.com/reports/3540663 Permissions Required

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-45286), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.