CVE-2025-66511CWE-330

CVE-2025-66511

Medium · published December 5, 2025

CVSS v3.1
4.8
EPSS
0%
Percentile
20.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.8 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00295 · 20.9th percentile
Weakness
CWE-330 · Use of Insufficiently Random Values
Published
2025-12-05T22:16Z
Affected products (1)
ProductVersionsFixed in
nextcloud/calendar≥ 6.0.0, < 6.0.36.0.3
References (4)
https://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fb · [email protected]https://github.com/nextcloud/calendar/pull/7659 · [email protected]https://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27 · [email protected]https://hackerone.com/reports/3385434 · [email protected]
EPSS history
Timeline
  • 05 DEC 16:42Z
    Nextcloud Calendar app used predictable proposal participant tokens
    cvelistv5