Medium 6.5Published Dec 5, 2025

CVE-2025-66511Nextcloud Calendar is a calendar app for Nextcloud.

Updated under an hour ago (2026-10-19 09:10 UTC)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for nextcloud calendar

Exploited in the last 30 days

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 request details and submit dates in meeting proposals. The tokens are not purely random generated. This vulnerability is fixed in 6.0.3.

CVSS: 6.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness (CWE): CWE-330
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Analyzed
Record last updated: Oct 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nextcloud calendar nextcloud:calendar	from 6.0.0 before 6.0.3	NVD

References

https://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fbpatch
https://github.com/nextcloud/calendar/pull/7659issue-tracking
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27patch, vendor-advisory
https://hackerone.com/reports/3385434permissions-required, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.