Vulnerability in Nextcloud Calendar
CVE-2025-66511
Nextcloud Calendar is a calendar app for Nextcloud. Prior to 6.0.3, the Calendar app generates participant tokens for meeting proposals using a hash function, allowing an attacker to compute valid participant tokens, which allowed them to…
EPSS: 0.003 (17.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Nextcloud Calendar
- Nextcloud Security-advisories — versions >= 6.0.0-rc.1, < 6.0.3
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 (Permissions Required, x_refsource_MISC, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66511?
- CVE-2025-66511 is a medium-severity vulnerability in Nextcloud Calendar, classified under Use of Insufficiently Random Values. CVSS score: 4.8/10. Published 2025-12-05.
- How severe is CVE-2025-66511?
- Medium severity. CVSS v3 base score is 4.8 out of 10.