What is the CVSS score of CVE-2025-66512?

CVE-2025-66512 has a CVSS 3.1 base score of 5.4 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L. EPSS exploitation probability: 0.0%.

Which versions of Nextcloud Server are affected by CVE-2025-66512?

Organizations using Nextcloud Server and Server Enterprise should be aware of moderate risk from CVE-2025-66512 rated CVSS 5.4. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2025-66512?

Within 30 days: Identify affected systems running Nextcloud Server and Server Enterprise and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Nextcloud Server CVE-2025-66512

EUVD-2025-201449 MEDIUM

Basic XSS (CWE-80)

2025-12-05 security-advisories@github.com

XSS Debian Nextcloud Server Nextcloud Suse

5.4

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

5.4 MEDIUM

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

SUSE

MEDIUM

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

Low

Lifecycle Timeline

EUVD ID Assigned

Mar 15, 2026 - 17:08 euvd

EUVD-2025-201449

Analysis Generated

Mar 15, 2026 - 17:08 vuln.today

Patch released

Mar 15, 2026 - 17:08 nvd

Patch available

CVE Published

Dec 05, 2025 - 17:16 nvd

MEDIUM 5.4

DescriptionGitHub Advisory

Nextcloud Server is a self hosted personal cloud system. In Nextcloud Server and Server Enterprise prior to 31.0.12 and 32.0.3, a missing sanitization allowed malicious users to circumvent the content security policy when a malicious user manages to trick a user it viewing an uploaded SVG outside of the Nextcloud Servers web page.

Analysis

Technical ContextAI

Cross-site scripting (XSS) allows injection of client-side scripts into web pages viewed by other users due to insufficient output encoding. This vulnerability is classified as Basic XSS (CWE-80).

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.