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Nextcloud ServerApplication · Nextcloud

CVE-2025-66512

MEDIUM · 6.1 CVSS v3.1 Published 2025-12-05
Fix available
A fix is available. Upgrade to 31.0.12 / 32.0.3 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nextcloud ServerApplication
Affected:>= 31.0.0, < 31.0.12>= 32.0.0, < 32.0.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 31.0.12 / 32.0.3 or later
Fixed in 31.0.1232.0.3
Vendor patch github.com →
Recommended fix High confidence

Nextcloud Server 31.0.12 or 32.0.3

  1. 1. Back up your current Nextcloud Server installation and database before proceeding.
  2. 2. Download Nextcloud Server 31.0.12 (if running version 31.x) or 32.0.3 (if running version 32.x) from the official Nextcloud downloads page.
  3. 3. Extract the new version to your server, preserving your config.php and data directory.
  4. 4. Run the upgrade command or navigate to the update URL to complete the upgrade process.
  5. 5. Clear any caching mechanisms (Redis, memcache, CDN caches) after upgrade.
  6. 6. Verify the upgrade was successful by logging in and checking the server version information.
  7. 7. Test that SVG file uploads are properly sanitized and CSP is enforced.
Caveat Patch releases typically have minimal breaking changes; review the Nextcloud changelog for any version-specific notes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-66512 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data