CVE-2025-66511 | BDVDB-2026-304086 Detail

nextcloudsecurity-advisories

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.

Impact#

Per CVSS v3.1: confidentiality impact low, integrity impact low, availability impact none. Attack vector: network.

Weaknesses#

CWE-330 Use of Insufficiently Random Values

References#

Exploit#

No public exploit known

History#

Version 12025-12-05Record published in the CVE List.

Published

Published: 2025-12-05
Last modified: 2025-12-05

Vendor information

Vendor: nextcloud
Product: security-advisories

All nextcloud vulnerabilities

Score

4.8 Medium

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 24.7.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Not classified

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 6.0.0-rc.1, < 6.0.3
Fixed
Not stated

Scoring System

CVSS v4.0

Not available

CVSS v3.1

4.8 Medium

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Metric breakdown
Attack Vector	Network
Attack Complexity	High
Privileges Required	None
User Interaction	None
Scope	Unchanged
Confidentiality	Low
Integrity	Low
Availability	None

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).