CVE-2025-66546

Nextcloud Calendar app allowed booking appointments without the generated token

3.3 Low

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.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: None
Availability: None

Exploit likelihood

0.15%Up 0.1 points since Dec 6, 2025

What each source reports

CVE List Score used 3.3

Nextcloud Calendar app allowed booking appointments without the generated token

Record: CVE-2025-66546
CVSS 3.1: 3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-639
Updated: 2026-11-02

EUVDEUVD-2025-201445 3.3

Record: EUVD-2025-201445
CVSS 3.1: 3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

NVD 3.3

Record: CVE-2025-66546
CVSS 3.1: 3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-639
Updated: 2026-11-02

OSV 3.3

Nextcloud Calendar app allowed booking appointments without the generated token

Record: CVE-2025-66546
CVSS 3.1: 3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-639
Updated: 2026-11-02

Affected products

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-66546 is a low vulnerability (CVSS 3.3) in Nextcloud Calendar, published December 5, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.15%, the 4th percentile. No source names a fixed version.