CVE-2025-66550— Nextcloud Calendar attachments of local files are offered to downloaded
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I. Basic Information for CVE-2025-66550
Vulnerability Information
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Vulnerability Title
Nextcloud Calendar attachments of local files are offered to downloaded
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
非预期数据类型处理不恰当
Source: NVD (National Vulnerability Database)
Vulnerability Title
Nextcloud Calendar 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Nextcloud Calendar是Nextcloud开源的一个日历应用程序。 Nextcloud Calendar 4.7.17之前版本和5.2.4之前版本存在安全漏洞，该漏洞源于恶意用户可创建特制附件，可能导致文件被自动下载。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| nextcloud | security-advisories | >= 5.0.0-rc.1, < 5.2.4 | - |
II. Public POCs for CVE-2025-66550
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · nextcloud · 2025-12-05 · 19 CVEs total
| CVE-2025-66551 | 6.3 MEDIUM | Nextcloud Tables is missing an ownership check which allows moving columns into tables of |
| CVE-2025-66512 | 5.4 MEDIUM | Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud |
| CVE-2025-66557 | 5.4 MEDIUM | Nextcloud Deck app allowed user with "Can share" permission to modify permissions of other |
| CVE-2025-66511 | 4.8 MEDIUM | Nextcloud Calendar app used predictable proposal participant tokens |
| CVE-2025-66510 | 4.5 MEDIUM | Nextcloud Server Contacts Search allowed users to retrieve contact information of other us |
| CVE-2025-66553 | 4.3 MEDIUM | Nextcloud Tables app allowed users to view columns metadata information of any table |
| CVE-2025-66547 | 4.3 MEDIUM | Nextcloud Server users can modify tags on files that do not belong to them |
| CVE-2025-66552 | 4.3 MEDIUM | Nextcloud Server admin_audit does not log all actions on files in groupfolders |
| CVE-2025-66513 | 4.3 MEDIUM | Nextcloud Tables app share information not limited to relevant users |
| CVE-2025-66514 | 3.5 LOW | Nextcloud Mail stored HTML injection in subject text |
| CVE-2025-66545 | 3.5 LOW | Nextcloud Groupfolders users with read-only permissions for team folder can restore delete |
| CVE-2025-66554 | 3.5 LOW | Nextcloud Contacts vulnerable to Stored XSS in contacts app via organisation and title fie |
| CVE-2025-66556 | 3.5 LOW | Nextcloud talk allows participants to blindly delete poll drafts of other users by ID |
| CVE-2025-66548 | 3.3 LOW | Nextcloud Deck app allows to spoof file extensions by using RTLO characters |
| CVE-2025-66546 | 3.3 LOW | Nextcloud Calendar app allowed booking appointments without the generated token |
| CVE-2025-66558 | 3.1 LOW | Nextcloud Twofactor WebAuthn app was updated based on public key |
| CVE-2025-66515 | 2.7 LOW | Nextcloud Approval app allows users to request approval for other users file |
| CVE-2025-66549 | 2.4 LOW | Nextcloud Desktop discloses information when attempting to lock a file inside a end-to-end |
IV. Related Vulnerabilities
Same product: security-advisories
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Kiteworks Core has an OS Command Injection - CVE-2025-66558
Nextcloud Twofactor WebAuthn app was updated based on public
Same vendor: nextcloud
- CVE-2025-66558
Nextcloud Twofactor WebAuthn app was updated based on public - CVE-2025-66556
Nextcloud talk allows participants to blindly delete poll dr - CVE-2025-66554
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Nextcloud Desktop discloses information when attempting to l - CVE-2025-66545
Nextcloud Groupfolders users with read-only permissions for
Same weakness: CWE-241
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