CVE-2025-66512

Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud

5.4 Medium

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required

What an attacker can affect

Confidentiality: None
Integrity: Low
Availability: Low

Exploit likelihood

0.30%Up 0.3 points since Dec 6, 2025

What each source reports

CVE List Score used 5.4

Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud

Record: CVE-2025-66512
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Weakness: CWE-80
Updated: 2026-11-02

EUVDEUVD-2025-201449 5.4

Record: EUVD-2025-201449
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Updated: 2026-11-02

NVD 5.4

Record: CVE-2025-66512
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-80, CWE-79
Updated: 2026-11-02

OSV 5.4

Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud

Record: CVE-2025-66512
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Weakness: CWE-80
Updated: 2026-11-02

Affected products

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-66512 is a medium vulnerability (CVSS 5.4) in Nextcloud Server, published December 5, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 22nd percentile. No source names a fixed version.