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CVE-2025-66512

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Date: December 5, 2025

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.

Severity Score

Related Resources (6)

https://github.com/nextcloud/viewer/pull/3023
https://hackerone.com/reports/3357808
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qcw2-p26m-9gc5
https://nvd.nist.gov/vuln/detail/CVE-2025-66512
https://github.com/nextcloud/viewer/commit/5044a27d61bc40c0f134298d36af91f865335b63
https://www.mend.io/vulnerability-database/CVE-2025-66512

Severity Score

Weakness Type (CWE)

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CWE-79

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

CWE-80

Top Fix

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Upgrade Version

Upgrade to version https://github.com/nextcloud/viewer.git - v32.0.3;https://github.com/nextcloud/viewer.git - v31.0.12

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CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): LOW
Privileges Required (PR): NONE
User Interaction (UI): REQUIRED
Scope (S): CHANGED
Confidentiality (C): LOW
Integrity (I): LOW
Availability (A): NONE

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