CVE-2025-66550

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

External lookup

Potential internet exposure

Potential exposure only — not proof of vulnerability.Shodan results indicate potentially internet-exposed products, not confirmed vulnerable systems. They do not confirm that any returned system is vulnerable to CVE-2025-66550.

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Product CPE queries

Derived from this CVE's existing NVD CPE 2.3 records; the application, operating-system, or hardware part is retained.

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Exact CVE query

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Metadata

Canonical fields

NVD status

Unavailable

Published

Dec 5, 2025

Modified

Jun 17, 2026

Official record

Authoritative NVD record

CVSS vector

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

CWE IDs

Vendor classifications

How this vector reads

CVSS 3.1 base metrics decoded below. This explanation does not recalculate or change the NVD score.

Attack Vector (AV): Network. The vulnerable system can be reached across network boundaries.
Attack Complexity (AC): Low. No special conditions beyond the attacker-controlled steps are required.
Privileges Required (PR): Low. The attacker needs basic user-level privileges.
User Interaction (UI): Required. Another user must take an action for exploitation to succeed.
Scope (S): Unchanged. Impacts remain within the vulnerable security authority.
Confidentiality Impact (C): None. There is no direct impact to this security property.
Integrity Impact (I): High. There is a total or serious impact to this security property.
Availability Impact (A): None. There is no direct impact to this security property.

Signals

Exploitation indicators

0 stored signals · no KEV · 0 OTX pulses