CVE-2025-66550 json
Nextcloud Calendar attachments of local files are offered to downloaded
published 2025-12-05 11 mo ago modified 2026-10-18 22 d ago also EUVD-2025-201443
- cvss
- 5.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 30%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- nextcloud calendar 4.7.17, 5.2.4
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 11 mo ago
Exploit prediction
0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N |
Affected products
- nextcloud security-advisories
Classification
- Weakness
-
- CWE-241 Improper Handling of Unexpected Data Type
References
-
github.com
/nextcloud/calendar/pull/6971
issue-tracking
-
github.com
/nextcloud/calendar/commit/63a6c398db01391eb9fd5297a0d4c3d6e614f769
patch
-
github.com
/nextcloud/security-advisories/security/advisories/GHSA-f29c-ppmv-8mcv
patch, vendor-advisory
-
hackerone.com
/reports/3112033
issue-tracking, vendor-advisory
Sources
- CVE List CVE-2025-66550
- NVD CVE-2025-66550
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.