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.
Published: 2025-12-05
Score: 4.8 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories

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History

Wed, 10 Dec 2025 16:15:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*

Fri, 05 Dec 2025 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Nextcloud
Nextcloud calendar
Vendors & Products Nextcloud
Nextcloud calendar

Fri, 05 Dec 2025 17:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 05 Dec 2025 16:45:00 +0000

Type Values Removed Values Added
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.
Title Nextcloud Calendar app used predictable proposal participant tokens
Weaknesses CWE-330
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}


Subscriptions

Nextcloud Calendar
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-12-05T16:53:52.674Z

Reserved: 2025-12-03T15:28:02.991Z

Link: CVE-2025-66511

cve-icon Vulnrichment

Updated: 2025-12-05T16:53:50.036Z

cve-icon NVD

Status : Analyzed

Published: 2025-12-05T17:16:04.797

Modified: 2025-12-10T16:14:27.230

Link: CVE-2025-66511

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2025-12-05T20:56:08Z

Weaknesses