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Nextcloud ServerApplication · Nextcloud

CVE-2023-39963

HIGH · 7.8 CVSS v3.1 Published 2023-08-10
Fix available
A fix is available. Upgrade to 20.0.14.15 / 21.0.9.13 or later.
See remediation →
81/100
Remediation priority · High
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 provides data storage for Nextcloud, an open source cloud platform. Starting in version 20.0.0 and prior to versions 20.0.14.15, 21.0.9.13, 22.2.10.14, 23.0.12.8, 24.0.12.5, 25.0.9, 26.0.4, and 27.0.1, a missing password confirmation allowed an attacker, after successfully stealing a session from a logged in user, to create app passwords for the victim. Nextcloud server versions 25.0.9, 26.0.4, and 27.0.1 and Nextcloud Enterprise Server versions 20.0.14.15, 21.0.9.13, 22.2.10.14, 23.0.12.9, 24.0.12.5, 25.0.9, 26.0.4, and 27.0.1 contain a patch for this issue. No known workarounds are available.

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
How this class of weakness works · CWE-284

The application fails to correctly restrict what a user can do or reach, so functions or resources are available to people who should not have them. Attackers simply probe for the paths where the check is missing or wrong. The fix is to enforce access-control decisions consistently on every request, evaluated against the acting user rather than assumed from context.

General guidance for the improper access control class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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:>= 20.0.0, < 20.0.14.15>= 21.0.0, < 21.0.9.13>= 22.0.0, < 22.2.10.14>= 23.0.0, < 23.0.12.9>= 24.0.0, < 24.0.12.5>= 25.0.0, < 25.0.9>= 26.0.0, < 26.0.4= 27.0.0

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
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 20.0.14.15 / 21.0.9.13 / 22.2.10.14 or later
Fixed in 20.0.14.1521.0.9.1322.2.10.14
Vendor patch github.com →
Recommended fix High confidence

Upgrade to Nextcloud Server 27.0.1 (or latest supported 27.x), or for longer-term support use 24.0.12.5 or 25.0.9 depending on your support requirements

  1. 1. Identify the currently installed Nextcloud Server version using the web interface (Settings > Administration > Overview) or by checking the version file in the Nextcloud installation directory.
  2. 2. Determine which supported release branch is appropriate for your environment based on your current version and support lifecycle.
  3. 3. Create a complete backup of the Nextcloud database, data directory, and configuration files before proceeding with the upgrade.
  4. 4. Put the Nextcloud server into maintenance mode to prevent user activity during upgrade.
  5. 5. Follow the official Nextcloud upgrade documentation to upgrade to one of the fixed versions: 20.0.14.15, 21.0.9.13, 22.2.10.14, 23.0.12.9, 24.0.12.5, 25.0.9, 26.0.4, or 27.0.1.
  6. 6. After upgrading, verify that the password confirmation is now required when creating app passwords in Settings > Security > App passwords.
  7. 7. Disable maintenance mode and test that the security fix is functioning correctly.
Caveat Major version upgrades may require checking app compatibility; review Nextcloud app ecosystem for any incompatible apps 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 $1,950. 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-2023-39963 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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