Craft CMS's mass assignment via id in newAttributes during bulk duplicate overwrites existing elements

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-50281: 0.43% estimated exploitation activity in the next 30 days; percentile 37.19 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary There is a mass-assignment flaw in the bulk-duplicate element action. Alice, holding only the permission to duplicate an entry she owns, submits an arbitrary id through the newAttributes request parameter. The duplication routine overrides its own id = null reset with that value and writes Alice’s attributes into Bob’s existing entry row. Details ElementsController::beforeAction() (src/controllers/ElementsController.php:119-124) pulls the request body into $this-attributes and rejects requests that ship an id or canonicalId key at the top level: The check inspects only the top-level payload. actionBulkDuplicate() (src/controllers/ElementsController.php:1708-1749) reads a separate newAttributes array and passes it straight through to the service layer: Elements::duplicateElement() (src/services/Elements.php:1814-1840) clones the source element, sets id to null, and then hands the attacker's array to Craft::configure(): Craft::configure() overwrites the reset id with any…

Published by the source

2 Jul 2026, 20:03 UTC

Last modified by the source

2 Jul 2026, 20:03 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-x5m4-g2cq-52pq

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# Patch Next advisory brief: CVE-2026-50281

Advisory: Craft CMS's mass assignment via id in newAttributes during bulk duplicate overwrites existing elements
IDs: CVE-2026-50281, GHSA-x5m4-g2cq-52pq
Record: https://patchnext.com/advisories/cve-2026-50281 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: craftcms/cms 5.9.21. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist craftcms/cms: affected >= 5.7.0, < 5.9.21; fixed in 5.9.21

## Suggested inspection (read-only)
- Packagist craftcms/cms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on craftcms/cms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-x5m4-g2cq-52pq (GitHub-reviewed advisory GHSA-x5m4-g2cq-52pq lists affected ranges: Packagist craftcms/cms >=5.7.0 <5.9.21)

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