craftcms/cms security advisory

CVE-2026-50281: Craft CMS's mass assignment via id in newAttributes during bulk duplicate overwrites existing elements

CVE-2026-50281 is a high-severity mass assignment vulnerability in the PHP package craftcms/cms (CVSS 7.1), published 2 July 2026. It is fixed in 5.9.21; earlier versions are affected. Exploiting it needs a low-privilege user account.

high 7.1 published 2026-07-02 · updated 2026-10-25

Affected versions: >= 5.7.0, < 5.9.21
Fixed in: 5.9.21
Newest release: 5.12.0
Severity: High · CVSS 7.1
Type: Mass assignment
CWE-915
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your craftcms/cms version affected?

Run composer show craftcms/cms in your project, then enter the version. We check it against this and every other known craftcms/cms advisory.

Who can exploit CVE-2026-50281

Access: A normal, low-privilege user account in the app.

CVSS vector (scored by GitHub): 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

Your app is only exposed if it uses the affected part of craftcms/cms. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-50281 in craftcms/cms

Find the installed version: composer show craftcms/cms. If you never required it yourself, composer why craftcms/cms shows which package pulls it in.
Update it: composer update craftcms/cms --with-all-dependencies. You need 5.9.21 or newer.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "craftcms/cms": "^5.9.21" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-50281.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for mass assignment issues while the upgrade waits. None of it replaces the fix.

Fill models only from validated input with an explicit list of allowed fields.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-50281 advisory

Craft CMS is a content management system (CMS). Versions 5.7.0 and above, prior to 5.9.21 contain a mass-assignment flaw in the bulk-duplicate element action. An attacker who is only able to duplicate their own entires can submit an arbitrary id through the newAttributes request parameter. The duplication routine overrides its own id = null reset with that value and writes the attacker's attributes into the victim's existing entry row. ElementsController::beforeAction() pulls the request body into $this->_attributes and rejects requests that ship an id or canonicalId key at the top level, actionBulkDuplicate(), reads a separate newAttributes array and passes it straight through to the service layer. Elements::duplicateElement() clones the source element, sets id to null, and then hands the attacker's array to Craft::configure(), which overwrites the reset id with any numeric value inside $newAttributes. PHP Yii's saveElement() then performs an UPDATE against the row with that primary key instead of an INSERT. The attackers's title, slug, authorId, postDate, and UID land on the victim's entry. safeAttributes() on Entry includes id because the base element model exposes it, so the Collection::only() filter does not strip it. This issue has been fixed in version 5.9.21.

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-50281. Advisory title: “Craft CMS's mass assignment via id in newAttributes during bulk duplicate overwrites existing elements”.

References

GitHub advisory GHSA-x5m4-g2cq-52pq github.com
Fix commit 8f6587c github.com

Other craftcms/cms advisories

critical Craft CMS: Passkey login accepts replayed WebAuthn assertions 2026-08-07
medium CVE-2026-72779: Craft CMS: Arbitrary file read via SplFileObject in non-sandboxed template contexts 2026-08-06
medium CVE-2026-72782: Craft CMS: Authenticated leak of secret environment variables 2026-08-06
medium CVE-2026-72785: Craft CMS: Authorization bypass: view-only Categories user can modify category structure via structures/move-element 2026-08-06
medium CVE-2026-14794: Craft CMS: Missing authorization check allows non-admin control panel users access to user registration metrics 2026-08-06
low CVE-2026-72783: Craft CMS: Incorrect path validation could potentially lead to path traversal 2026-08-06

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.