Nextcloud Deck app allows to spoof file extensions by using RTLO characters

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-66548
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-12-05 18:15:57 UTC
Updated2026-10-15 21:10:00 UTC
DescriptionNextcloud 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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-116 | CWE-116 CWE-116: Improper Encoding or Escaping of Output

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
3.1[email protected]Secondary3.3LOWCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
3.1CNADECLARED3.3LOWCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Nextcloud Deck All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nextcloud Security-advisories affected >= 1.15.0-beta.1, < 1.15.1 Not specified
CNA Nextcloud Security-advisories affected >= 1.14.0-beta.1, < 1.14.4 Not specified
CNA Nextcloud Security-advisories affected < 1.12.7 Not specified

References

ReferenceSourceLinkTags
hackerone.com/reports/2326618 [email protected] hackerone.com Permissions Required, Vendor Advisory
github.com/nextcloud/deck/commit/afa95d3c507465b9d31af7c88c69b76711ef185a [email protected] github.com Patch
github.com/nextcloud/security-advisories/security/advisories/GHSA-xjvq-x... [email protected] github.com Patch, Vendor Advisory
github.com/nextcloud/deck/pull/6671 [email protected] github.com Issue Tracking
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