XSS in Nextcloud Server
CVE-2025-66512
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.
EPSS: 0.002 (15.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L.
Affected products
- Nextcloud Nextcloud_server
- Nextcloud Security-advisories — versions >= 32.0.0beta1, < 32.0.3, < 31.0.12
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66512?
- CVE-2025-66512 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS). CVSS score: 5.4/10. Published 2025-12-05.
- How severe is CVE-2025-66512?
- Medium severity. CVSS v3 base score is 5.4 out of 10.