Medium 5.7Published Dec 5, 2025

CVE-2025-66550Nextcloud Calendar attachments of local files are offered to downloaded

Updated under an hour ago (Oct 27, 2026, 10:50 AM ET)

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It affects nextcloud security-advisories and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for nextcloud security-advisories

Exploited in the last 30 days

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: 5.7 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-241
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Dec 5, 2025
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nextcloud security-advisories nextcloud:security_advisories (from the name)	from 5.0.0-rc.1, < 5.2.4; before 4.7.17	CNA record
nextcloud calendar nextcloud:calendar	from 4.0.0 before 4.7.17; from 5.0.0 before 5.2.4	NVD

References

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcv	x-refsource-confirm, patch, vendor-advisory
https://github.com/nextcloud/calendar/pull/6971	x-refsource-misc, issue-tracking
https://github.com/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769	x-refsource-misc, patch
https://hackerone.com/reports/3112033	x-refsource-misc, issue-tracking, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.