CVE-2025-66550

MediumCVSS 5.7/10Last modified Oct 18, 2026

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.

Metrics

CVSS 3.1 5.7/10CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N

Weakness enumeration

CWE-241

Affected software

Vendor	Product	Versions
nextcloud	security-advisories	>= 5.0.0-rc.1, < 5.2.4; < 4.7.17

References

https://github.com/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769Patch
https://github.com/nextcloud/calendar/pull/6971Issue Tracking
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcvPatch, Vendor Advisory
https://hackerone.com/reports/3112033Issue Tracking, Vendor Advisory

Timeline

Published: Dec 5, 2025
Last modified: Oct 18, 2026
NVD status: Analyzed

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