---
cve: "CVE-2025-66550"
severity: "MEDIUM"
cvss: 5.7
epss: "0.3%"
vendor: "nextcloud"
kev: false
exploited: false
published: "2025-12-05 17:16:05"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-21T09:23:08+02:00"
---

# CVE-2025-66550

> 5.7 MEDIUM · 🧪 PoC

## Beschreibung

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-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Erforderlich | good |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 44423c0b8f0d903102f2bbf7a12808b8ac3da64d (Commit)
- f823d93dd3ac0b759c24c769832277bf94e3081d (Commit)

## Referenzen

- <https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcv>
- <https://github.com/nextcloud/calendar/pull/6971>
- <https://github.com/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769>
- <https://hackerone.com/reports/3112033>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2025-66550) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_