CVE-2025-66550 Details
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.
A vulnerability exists in Nextcloud Calendar versions 4.0.0 through 4.7.16 and 5.0.0 through 5.2.3, allowing files to be downloaded automatically from the same Nextcloud server without user confirmation. This issue arises when a malicious user creates a calendar event with a crafted attachment linking to a file download. The vulnerability has been addressed in versions 4.7.17 and 5.2.4.
Users are advised to update the Nextcloud Calendar app to version 4.7.17 or 5.2.4. If an immediate update is not possible, the Calendar app can be disabled as a temporary workaround.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Dec 5, 2025References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769 | [email protected] | Patch |
| https://github.com/nextcloud/calendar/pull/6971 | [email protected] | Issue Tracking |
| https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcv | [email protected] | PatchVendor Advisory |
| https://hackerone.com/reports/3112033 | [email protected] | Issue TrackingVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-241 | Improper Handling of Unexpected Data Type | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| nextcloud calendar | >= 4.0.0, < 4.7.17 >= 5.0.0, < 5.2.4 |
CPE
Remediation
| |
Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Dec 10, 2025 | Initial Analysis | [email protected] |
| Dec 5, 2025 | New CVE Received | [email protected] |