---
id: CVE-2026-50281
title: >-
  Craft CMS's mass assignment via id in newAttributes during bulk duplicate
  overwrites existing elements
summary: >-
  Craft CMS's mass assignment via id in newAttributes during bulk duplicate
  overwrites existing elements
severity: high
cwe:
  - CWE-915
vendor: craftcms
product: craftcms/cms
ecosystem: composer
affected:
  - 'craftcms/cms >= 5.7.0, < 5.9.21'
patched:
  - craftcms/cms 5.9.21
published: '2026-07-02'
updated: '2026-07-02'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-x5m4-g2cq-52pq'
references:
  - url: 'https://github.com/craftcms/cms/security/advisories/GHSA-x5m4-g2cq-52pq'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-50281'
  - url: >-
      https://github.com/craftcms/cms/commit/8f6587c25050bbb6e080d59c71f6bb8932fc8600
  - url: 'https://github.com/advisories/GHSA-x5m4-g2cq-52pq'
tags:
  - ghsa
  - composer
ingestedAt: '2026-07-02T20:42:45.824Z'
epss: 0.00429
epssPercentile: 0.34419
---

## Overview

## 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:

```php
$this->_attributes = $this->request->getBodyParams();

// No funny business
if (isset($this->_attributes['id']) || isset($this->_attributes['canonicalId'])) {
    throw new BadRequestHttpException('Changing an element’s ID is not allowed.');
}
```

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:

```php
$elementInfo = $this->request->getRequiredBodyParam('elements');
$newAttributes = $this->request->getRequiredBodyParam('newAttributes');
...
$safeNewAttributes = Collection::make($newAttributes)
    ->only($element->safeAttributes())
    ->all();
...
$newElement = $elementsService->duplicateElement(
    $element,
    $safeNewAttributes + $element::baseBulkDuplicateAttributes(),
    false,
    checkAuthorization: true,
);
```

`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()`:

```php
$mainClone = clone $element;
$mainClone->id = null;
$mainClone->uid = StringHelper::UUID();
...
Craft::configure($mainClone, ArrayHelper::merge(
    $newAttributes,
    $siteAttributes[$mainClone->siteId] ?? [],
));
```

`Craft::configure()` overwrites the reset `id` with any numeric value inside `$newAttributes`. Yii's `saveElement()` then performs an UPDATE against the row with that primary key instead of an INSERT. Alice's title, slug, authorId, postDate, and UID land on Bob’s entry.

`safeAttributes()` on `Entry` includes `id` because the base element model exposes it, so the `Collection::only()` filter does not strip it.

## Impact

A low-privileged author overwrites any other element (entries, categories, users that share the Entry element table inheritance) by predicting or enumerating element IDs. Content integrity on the entire install breaks. The attack requires only the ability to duplicate one entry Alice already owns.

## Affected packages

- `craftcms/cms >= 5.7.0, < 5.9.21`

## Remediation

Upgrade to a patched release:

- `craftcms/cms 5.9.21`