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.

CVSS 3.1

6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.3% chance of exploitation in the next 30 days; higher than 20% of CVEs (scores of 2026-10-25)

CWEs

CWE-79, CWE-80

Published

2025-12-05

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

Affected

• nextcloud:nextcloud_server

References

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qcw2-p26m-9gc5
• https://github.com/nextcloud/viewer/commit/5044a27d61bc40c0f134298d36af91f865335b63
• https://github.com/nextcloud/viewer/pull/3023
• https://hackerone.com/reports/3357808

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