Medium severity · published Dec 5, 2025
CVE-2025-66512
Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud
6.1
CVSS
0.3%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SE
security-advisories · nextcloud
>= 32.0.0beta1, < 32.0.3; < 31.0.12 · source: vendor
NS
Nextcloud Server · Nextcloud
31.0.0 before 31.0.12; 31.0.0 before 31.0.12; 32.0.0 before 32.0.3; 32.0.0 before 32.0.3 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66512
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66512
Patch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qcw2-p26m-9gc5
Patch
https://github.com/nextcloud/viewer/commit/5044a27d61bc40c0f134298d36af91f865335b63
Issue Tracking
https://github.com/nextcloud/viewer/pull/3023
Issue Tracking
https://hackerone.com/reports/3357808
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