CVE-2025-66511

Nextcloud Calendar app used predictable proposal participant tokens

Published: Dec 5, 2025Updated: Dec 10, 2025 Sources: CVE List NVD BDUCWE-330

4.8MEDIUM

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:HAttack Complexity

High

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:LConfidentiality

Low

I:LIntegrity

Low

A:NAvailability

None

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Weaknesses

CWE-330

Affected Products

nextcloud

oss-project·DEaka nextcloud server

calendarSaaSWeb App

Cloud & SaaS / saas-application

security-advisoriesSaaSSaaS Service

Cloud & SaaS / saas-application

ООО «Ред Софт»

commercial·RUaka red soft

РЕД ОСOn-premOS

Operating Systems / linux-distro

Nextcloud GmbH

commercial·DEaka nextcloud server, nextcloud enterprise server, nextcloud calendar

Nextcloud CalendarSaaS

Cloud & SaaS / saas-application

Exploitability

Official Patch Available

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Credential Access

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References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27

github.com

http://repo.red-soft.ru/redos/8.0/x86_64/updates/

repo.red-soft.ru

https://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fb

github.com

and 3 more references View all →

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