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Nextcloud ServerApplication · Nextcloud

CVE-2023-49791

MEDIUM · 5.4 CVSS v3.1 Published 2023-12-22
Fix available
A fix is available. Upgrade to 23.0.12.13 / 24.0.12.9 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable 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 provides data storage for Nextcloud, an open source cloud platform. In Nextcloud Server prior to versions 26.0.9 and 27.1.4; as well as Nextcloud Enterprise Server prior to versions 23.0.12.13, 24.0.12.9, 25.0.13.4, 26.0.9, and 27.1.4; when an attacker manages to get access to an active session of another user via another way, they could delete and modify workflows by sending calls directly to the API bypassing the password confirmation shown in the UI. Nextcloud Server versions 26.0.9 and 27.1.4 and Nextcloud Enterprise Server versions 23.0.12.13, 24.0.12.9, 25.0.13.4, 26.0.9, and 27.1.4 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:>= 23.0.0, < 23.0.12.13>= 24.0.0, < 24.0.12.9>= 25.0.0, < 25.0.13.4>= 26.0.0, < 26.0.9>= 27.0.0, < 27.1.4

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

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

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 23.0.12.13 / 24.0.12.9 / 25.0.13.4 or later
Fixed in 23.0.12.1324.0.12.925.0.13.4
Vendor patch github.com →
Recommended fix High confidence

Nextcloud Server 26.0.9 or 27.1.4 (or later)

  1. Identify the current Nextcloud Server version by checking the admin settings or config/version.php
  2. Review the Nextcloud Server changelog for the target fixed version (26.0.9 or 27.1.4 or later) for any breaking changes relevant to your setup
  3. Create a complete backup of the Nextcloud instance including the database and all data files
  4. Put the Nextcloud server into maintenance mode
  5. Upgrade Nextcloud Server to version 26.0.9 or 27.1.4 (or later) by running the standard upgrade command: occ upgrade or by using the web updater
  6. After upgrade completes, verify the version number matches the expected fixed version in admin settings
  7. Take the server out of maintenance mode with: occ maintenance:mode --off
  8. Test that workflow creation and modification now properly require password confirmation
Caveat Review Nextcloud changelog for any breaking changes between your current version and target version; minor point releases typically have minimal breaking changes

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-2023-49791 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
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