Description
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.
References (4)
Core 4
Core References
Patch, Vendor Advisory x_refsource_confirm
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27
Issue Tracking x_refsource_misc
https://github.com/nextcloud/calendar/pull/7659
Patch x_refsource_misc
https://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fb
Permissions Required, Vendor Advisory x_refsource_misc
https://hackerone.com/reports/3385434
Scores
CVSS v3
4.8
EPSS
0.0025
EPSS Percentile
15.5%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-330
Status
published
Products (1)
nextcloud/calendar
6.0.0 - 6.0.3
Published
Dec 05, 2025
Tracked Since
Feb 18, 2026