CVE-2025-66550 (GCVE-0-2025-66550)
Vulnerability from cvelistv5 – Published: 2025-12-05 16:56 – Updated: 2025-12-05 18:41
VLAI
EPSS
VEX
Title
Nextcloud Calendar attachments of local files are offered to downloaded
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.
Severity
5.7 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-12-05 18:37 UTC
CWE
- CWE-241 - Improper Handling of Unexpected Data Type
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/nextcloud/security-advisories/… | x_refsource_CONFIRM |
| https://github.com/nextcloud/calendar/pull/6971 | x_refsource_MISC |
| https://github.com/nextcloud/calendar/commit/63a6… | x_refsource_MISC |
| https://hackerone.com/reports/3112033 | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| nextcloud | security-advisories |
Affected:
>= 5.0.0-rc.1, < 5.2.4
Affected: < 4.7.17 |
guessed |
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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