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CVE-2025-66548— Nextcloud Deck app allows to spoof file extensions by using RTLO characters

Quick assessment

Affected
nextcloud security-advisories
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Deck是Nextcloud开源的一个看板风格的组织工具。旨在为与 Nextcloud 集成的团队进行个人规划和项目组织。 Deck 1.12.7之前版本、1.14.4之前版本和1.15.1之前版本存在安全漏洞，该漏洞源于文件扩展名可被伪造，可能导致用户下载恶意文件。

CVSS 3.3 · Low EPSS 0.15% · P4

Possible ATT&CK Techniques 1 AI

T1561.001 · Disk Content Wipe
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I. Basic Information for CVE-2025-66548

Vulnerability Information
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Vulnerability Title
Nextcloud Deck app allows to spoof file extensions by using RTLO characters
Source: CVE Program / CVE List V5
Vulnerability Description
Nextcloud Deck is a kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. Prior to 1.12.7, 1.14.4, and 1.15.1, file extension can be spoofed by using RTLO characters, tricking users into download files with a different extension than what is displayed. This vulnerability is fixed in 1.12.7, 1.14.4, and 1.15.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Deck 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Deck是Nextcloud开源的一个看板风格的组织工具。旨在为与 Nextcloud 集成的团队进行个人规划和项目组织。 Deck 1.12.7之前版本、1.14.4之前版本和1.15.1之前版本存在安全漏洞，该漏洞源于文件扩展名可被伪造，可能导致用户下载恶意文件。
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 >= 1.15.0-beta.1, < 1.15.1 -

II. Public POCs for CVE-2025-66548

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III. Intelligence Information for CVE-2025-66548

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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-2025-66550 5.7 MEDIUM Nextcloud Calendar attachments of local files are offered to downloaded
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-2025-66513 4.3 MEDIUM Nextcloud Tables app share information not limited to relevant users
CVE-2025-66552 4.3 MEDIUM Nextcloud Server admin_audit does not log all actions on files in groupfolders
CVE-2025-66547 4.3 MEDIUM Nextcloud Server users can modify tags on files that do not belong to them
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-2025-66546 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
Same vendor: nextcloud
Same weakness: CWE-116

V. Comments for CVE-2025-66548

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