CVE-2025-66546

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.19, 5.5.6, and 6.0.1, the calendar app allowed blindly booking appointments with a squential ID without known the appointment token. This vulnerability is fixed in 4.7.19, 5.5.6, and 6.0.1.

CVSS 3.1

3.3CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS

0.1% chance of exploitation in the next 30 days; higher than 3% of CVEs (scores of 2026-10-25)

CWE

CWE-639

Published

2025-12-05

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

Affected

• nextcloud:calendar

References

• https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3
• https://github.com/nextcloud/calendar/pull/7537
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95
• https://hackerone.com/reports/3275810

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