# 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…

Source: https://junglewise.ai/threats/cve-2025-66546-nextcloud-calendar-is-a-calendar-app-for-nextcloud-prior-to-4-7  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-05  
License: CC BY 4.0 with a link back

CVE-2025-66546 · Severity: low · CVSS 3.3 · Published 2025-12-05

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.

Technologies: [Nextcloud Calendar](https://junglewise.ai/threats/technologies/calendar). Vendors: [Nextcloud](https://junglewise.ai/threats/vendors/nextcloud).

## Quick answers

**Is CVE-2025-66546 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-66546 being exploited in the wild.

**How severe is CVE-2025-66546?** Low severity, with a CVSS score of 3.3, published 5 December 2025.

**Which products and versions are affected?** Nextcloud Calendar. The advisory does not name versions.

**Is there a fix for CVE-2025-66546?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2025-66546?** Check whether you run Nextcloud Calendar. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Nextcloud Calendar

## Related threats

- [Nextcloud Calendar user enumeration via attendee suggestion endpoint](https://junglewise.ai/threats/cve-2026-45286-nextcloud-calendar-user-enumeration-via-attendee-suggestion)
- [Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.17 and 5.2.4, when a malicious user creates a…](https://junglewise.ai/threats/cve-2025-66550-nextcloud-calendar-is-a-calendar-app-for-nextcloud-prior-to-4-7)
- [Nextcloud Calendar is a calendar app for Nextcloud. Prior to 6.0.3, the Calendar app generates participant tokens for…](https://junglewise.ai/threats/cve-2025-66511-nextcloud-calendar-is-a-calendar-app-for-nextcloud-prior-to-6-0-3)