Auth bypass in Nextcloud Calendar
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…
Vulnerability class: IDOR (Insecure Direct Object Reference)
EPSS: 0.001 (2.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Nextcloud Calendar — versions 6.0.0
- Nextcloud Security-advisories — versions >= 6.0.0-rc.1, < 6.0.1, >= 5.0.0-rc.1, < 5.5.6, >= 3.0.0-beta1, < 4.7.19
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66546?
- CVE-2025-66546 is a low-severity vulnerability in Nextcloud Calendar, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 3.3/10. Published 2025-12-05.
- How severe is CVE-2025-66546?
- Low severity. CVSS v3 base score is 3.3 out of 10.