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CVE-2025-66550

Nextcloud Calendar attachments of local files are offered to downloaded

Published: Dec 5, 2025Updated: Dec 10, 2025 Sources: CVE List NVD BDUCWE-241
NVD MITRE
5.7CVSSMEDIUM
EPSS Score
0.3%
Top 80.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.17 and 5.2.4, when a malicious user creates a calendar event with a crafted attachment that links to a download link of a file on the same Nextcloud server, the file would be downloaded without the user confirming the action. This vulnerability is fixed in 4.7.17 and 5.2.4.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:UC:NI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-241

Affected Products

РЕД ОСООО «Ред Софт»
On-premOS
Operating Systems / linux-distro
Nextcloud CalendarNextcloud GmbH
SaaS
Cloud & SaaS / saas-application
calendarnextcloud
On-prem
Cloud & SaaS / saas-application
security-advisoriesnextcloud
SaaSSaaS Service
Cloud & SaaS / saas-application
ооо «ред софт»commercialRUOperating Systemsaka red soft
nextcloud gmbhcommercialDECloud & SaaSaka nextcloud server, nextcloud enterprise server, nextcloud calendar
nextcloudoss-projectDECloud & SaaSaka nextcloud server

Exploitability

Official Patch Available

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcv
github.com
http://repo.red-soft.ru/redos/8.0/x86_64/updates/
repo.red-soft.ru
https://github.com/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769
github.com
and 3 more references View all →

Timeline

Published
Dec 5, 2025
Last Updated
Dec 10, 2025

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