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Nextcloud ServerApplication · Nextcloud

CVE-2021-32726

CRITICAL · 9.8 CVSS v3.1 Published 2021-07-12
Fix available
A fix is available. Upgrade to 19.0.13 / 20.0.11 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 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 Nextcloud package that handles data storage. In versions prior to 19.0.13, 20.011, and 21.0.3, webauthn tokens were not deleted after a user has been deleted. If a victim reused an earlier used username, the previous user could gain access to their account. The issue was fixed in versions 19.0.13, 20.0.11, and 21.0.3. There are no known workarounds.

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:< 19.0.13>= 20.0.0, < 20.0.11>= 21.0.0, < 21.0.3

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 19.0.13 / 20.0.11 / 21.0.3 or later
Fixed in 19.0.1320.0.1121.0.3
Vendor patch github.com →
Recommended fix High confidence

Upgrade to 21.0.3 (or the latest 21.x release), or 20.0.11 if staying on the 20.x branch, or 19.0.13 if staying on the 19.x branch

  1. 1. Back up your Nextcloud Server instance (database, config, and data directories) before upgrading.
  2. 2. Upgrade to one of the fixed versions: 19.0.13, 20.0.11, or 21.0.3.
  3. 3. If currently on version 18.x or lower, upgrade sequentially through major versions (e.g., 18.x -> 19.x -> 20.x -> 21.x) following Nextcloud's upgrade documentation to avoid compatibility issues.
  4. 4. After upgrading, verify that the webauthn tokens are properly cleaned up for deleted users by testing user deletion and recreation with the same username.
Caveat Nextcloud major version upgrades may introduce breaking changes; review the changelog for your target version and test in a staging environment first

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 $2,300. 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-2021-32726 in production — separate from our analysis above.

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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