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Nextcloud CVE-2025-66514

| EUVDEUVD-2025-201464 LOW
Cross-site Scripting (XSS) (CWE-79)
2025-12-05 security-advisories@github.com
3.5
CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY
3.5 LOW
AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

Lifecycle Timeline

4
EUVD ID Assigned
Mar 15, 2026 - 17:08 euvd
EUVD-2025-201464
Analysis Generated
Mar 15, 2026 - 17:08 vuln.today
Patch released
Mar 15, 2026 - 17:08 nvd
Patch available
CVE Published
Dec 05, 2025 - 18:15 nvd
LOW 3.5

DescriptionGitHub Advisory

Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.

Analysis

Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.

Technical ContextAI

Cross-site scripting (XSS) allows injection of client-side scripts into web pages viewed by other users due to insufficient output encoding.

RemediationAI

A vendor patch is available — apply it immediately. Encode all user-supplied output contextually (HTML, JS, URL). Implement Content Security Policy (CSP) headers. Use HTTPOnly and Secure cookie flags.

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CVE-2025-66514 vulnerability details – vuln.today

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