CVE-2025-66546

Name: CVE-2025-66546
Creator: NVD / NIST
Published: 2025-12-05T17:16:05.163+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

LOWCVSS 3.3/10EPSS 0.12%

Last modified Jun 17, 2026

CVE-2025-66546 is a low-severity vulnerability rated 3.3/10 on the CVSS scale. 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. EPSS estimates a 0.12% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

3.3/10

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

EPSS Probability

0.12%

2.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-639

Affected Software

Vendor	Product	Versions
Nextcloud	Calendar	>= 4.0.0, < 4.7.19
Nextcloud	Calendar	>= 5.0.0, < 5.5.6
Nextcloud	Calendar	6.0.0

References

https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3Patch
https://github.com/nextcloud/calendar/pull/7537Issue Tracking
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95Patch, Vendor Advisory
https://hackerone.com/reports/3275810Issue Tracking, Vendor Advisory

Timeline

Published: Dec 5, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-66546?

How severe is CVE-2025-66546?

CVE-2025-66546 has a CVSS score of 3.3/10 (LOW severity). The EPSS model estimates a 0.12% probability of exploitation in the next 30 days.

How do I fix CVE-2025-66546?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-66546?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST