CVE•Published 2025-12-05•Modified 2026-10-18•0 articles on news•4 live references•NVD data

CVE-2025-66550Nextcloud · Calendar

Vulnerability data via NVD (ingested)

CVSS v3.1

5.7

MEDIUM

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

EPSS percentile

Exploit Prediction Scoring System · top 74% of all CVEs

Weaknesses (CWE)

CWE-241Improper Handling of Unexpected Data Type

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.

Timeline

Published 2025-12-05

Modified 2026-10-18

External references

NVD MITRE Exploit-DB VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2025-66550

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Nextcloud Calendar"

All exposed Nextcloud Calendar instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Calendar"

HTTP body or banner mentions "Calendar" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2025-66550