dbcve.org
Nextcloud ServerApplication · Nextcloud

CVE-2026-45281

HIGH · 8.1 CVSS v3.1 Published 2026-06-01
Fix available
A fix is available. Upgrade to 21.0.9.23 / 22.2.10.39 or later.
See remediation →
87/100
Remediation priority · High
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 is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23

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-639

The application uses a user-supplied identifier to look up a record without checking that the requester actually owns it, so changing the identifier in a request returns someone else's data. This is the classic insecure-direct-object-reference — the change-the-ID-in-the-URL bug. Remediation is authorizing every object access against the acting user, not merely confirming they are logged in.

General guidance for the authorization bypass (idor) 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:>= 32.0.0, < 32.0.9>= 33.0.0, < 33.0.3>= 21.0.0, < 21.0.9.23>= 22.0.0, < 22.2.10.39>= 23.0.0, < 23.0.12.35>= 24.0.0, < 24.0.12.34>= 25.0.0, < 25.0.13.29>= 26.0.0, < 26.0.13.26>= 27.0.0, < 27.1.11.26>= 28.0.0, < 28.0.14.17>= 29.0.0, < 29.0.16.16>= 30.0.0, < 30.0.17.9

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
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 21.0.9.23 / 22.2.10.39 / 23.0.12.35 or later
Fixed in 21.0.9.2322.2.10.3923.0.12.35
Vendor patch github.com →
Recommended fix High confidence

Nextcloud Server 32.0.9 or 33.0.3 (depending on current major version); 21.0.9.23 or 22.2.10.39 for older branches

  1. 1. Identify the currently installed Nextcloud Server version using the admin settings or occ command: occ --version
  2. 2. For Nextcloud Server 32.x versions (32.0.0 - 32.0.8): Upgrade to version 32.0.9
  3. 3. For Nextcloud Server 33.x versions (33.0.0 - 33.0.2): Upgrade to version 33.0.3
  4. 4. For Nextcloud Server 21.x versions: Upgrade to version 21.0.9.23
  5. 5. For Nextcloud Server 22.x versions: Upgrade to version 22.2.10.39
  6. 6. Before upgrading, backup the Nextcloud data directory and database
  7. 7. Run the upgrade following Nextcloud's standard upgrade documentation
  8. 8. Verify the upgrade was successful and test calendar functionality
Caveat Standard Nextcloud upgrade considerations apply - review migration notes for your version jump, test in staging 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 $1,950. Get the upgrade done

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-45281 — 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-2026-45281 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