dbcve.org
Nextcloud ServerApplication · Nextcloud

CVE-2021-32654

CRITICAL · 9.1 CVSS v3.1 Published 2021-06-01
Fix available
A fix is available. Upgrade to 19.0.11 / 20.0.10 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 Nextcloud package that handles data storage. In versions prior to 19.0.11, 20.0.10, and 21.0.2, an attacker is able to receive write/read privileges on any Federated File Share. Since public links can be added as federated file share, this can also be exploited on any public link. Users can upgrade to patched versions (19.0.11, 20.0.10 or 21.0.2) or, as a workaround, disable federated file sharing.

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 · high confidence

Nextcloud Server versions prior to 19.0.11, 20.0.10, and 21.0.2 contain an authorization bypass vulnerability allowing attackers to gain unauthorized write/read privileges on any Federated File Share. Since public links can be added as federated file shares, this vulnerability also affects public link shares, enabling attackers to read or modify files they should not have access to.

MitigationUpgrade to patched versions (19.0.11, 20.0.10, or 21.0.2). As a workaround, disable federated file sharing until patching can be completed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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:< 19.0.11>= 20.0.0, < 20.0.10>= 21.0.0, < 21.0.2

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Nextcloud Server version
    Log into the Nextcloud web interface as an administrator, navigate to Settings > Administration > Overview, and note the version number displayed. Alternatively, inspect the file /nextcloud/version.php on the server and look for the $OC_Version variable.
    Affected if The installed version is less than 19.0.11, OR between 20.0.0 and 20.0.9 inclusive, OR between 21.0.0 and 21.0.1 inclusive.
  2. Verify if Federated File Sharing is enabled
    In the Nextcloud web interface, go to Settings > Administration > Sharing > Federated file sharing. Check whether the 'Enable federated file sharing' option is turned on.
    Affected if Federated file sharing is currently enabled.
  3. Confirm use of public link shares
    In the Nextcloud web interface, navigate to the Files app and review the sharing column for any folders or files shared via public link. Alternatively, go to Settings > Administration > Sharing and verify if public link sharing is allowed.
    Affected if Any public link shares exist, or public link sharing is permitted in the sharing settings.

You are affected if your Nextcloud Server version falls within the vulnerable ranges AND federated file sharing is enabled, since this is the attack vector for the authorization bypass.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 19.0.11 / 20.0.10 / 21.0.2 or later
Fixed in 19.0.1120.0.1021.0.2
Interim mitigation

Upgrade to patched versions (19.0.11, 20.0.10, or 21.0.2). As a workaround, disable federated file sharing until patching can be completed.

Recommended fix High confidence

Upgrade to Nextcloud Server 19.0.11, 20.0.10, or 21.0.2 (whichever corresponds to your major version)

  1. 1. Back up your Nextcloud Server installation and database before upgrading.
  2. 2. Identify your current Nextcloud version in the administrative web interface (Settings > Administration > Overview).
  3. 3. Based on your current version, plan your upgrade path: if below 19.0.11, upgrade to 19.0.11; if >= 20.0.0 and < 20.0.10, upgrade to 20.0.10; if >= 21.0.0 and < 21.0.2, upgrade to 21.0.2.
  4. 4. Download the appropriate Nextcloud Server release from the official Nextcloud server download page.
  5. 5. Stop the web server (e.g., apache2, nginx) and PHP-FPM services.
  6. 6. Replace the current Nextcloud files with the new version files, preserving the config/ and data/ directories.
  7. 7. Run the Nextcloud upgrade command: 'sudo -u www-data php occ upgrade' (adjust the user to match your web server user).
  8. 8. Restart the web server and PHP-FPM services.
Caveat Review Nextcloud changelists for major version upgrades for any breaking changes between versions; test in a staging environment before production deployment

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

Fix this in Nextcloud Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-32654 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-32654 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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