drupal/core security advisory

CVE-2026-6366: Drupal core allows Object Injection

CVE-2026-6366 is a medium-severity PHP object injection vulnerability in the PHP package drupal/core (CVSS 6.6), published 19 May 2026. It is fixed in 10.5.9, 10.6.7, 11.2.11 and 11.3.7, one per release line; earlier versions on each line are affected. Exploiting it needs an admin-level account.

medium 6.6 published 2026-05-19 · updated 2026-07-24

Affected versions: >= 8.0.0, < 10.5.9
>= 10.6.0, < 10.6.7
>= 11.0.0, < 11.2.11
>= 11.3.0, < 11.3.7
Fixed in: 10.5.9, 10.6.7, 11.2.11, 11.3.7
Newest release: 11.4.11
Severity: Medium · CVSS 6.6
Type: PHP object injection
CWE-915
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your drupal/core version affected?

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

Who can exploit CVE-2026-6366

Access: A high-privilege account in the app, such as an admin.
Conditions: It only works under specific conditions the attacker does not fully control (CVSS rates the attack as high complexity).

CVSS vector (scored by CISA ADP): CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Your app is only exposed if it uses the affected part of drupal/core. 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-2026-6366 in drupal/core

Find the installed version: composer show drupal/core. If you never required it yourself, composer why drupal/core shows which package pulls it in.
Update it: composer update drupal/core --with-all-dependencies. You need the fixed version for your release line (10.5.9, 10.6.7, 11.2.11 and 11.3.7).
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "drupal/core": "^11.3.7" 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-2026-6366.
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 PHP object injection issues while the upgrade waits. None of it replaces the fix.

Never pass user-controlled data to unserialize() or to template rendering, and restrict who can edit templates or settings.
Put a web application firewall in front of the app and watch for new PHP files or admin users.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-6366 advisory

Improperly Controlled Modification of Dynamically-Determined Object Attributes vulnerability in Drupal Drupal core allows Object Injection. This issue affects Drupal core: from 8.0.0 before 10.5.9, from 10.6.0 before 10.6.7, from 11.0.0 before 11.2.11, from 11.3.0 before 11.3.7.

Description from the CVE record, published by Drupal (the CVE Numbering Authority), via the NVD entry for CVE-2026-6366. Advisory title: “Drupal core allows Object Injection”.

References

GitHub advisory GHSA-xmjc-63pr-2mpg github.com
drupal.org www.drupal.org

Other drupal/core advisories

critical CVE-2026-9082: Drupal Core has a SQL Injection issue 2026-05-20
medium CVE-2026-6365: Drupal core is Vulnerable to Cross-Site Scripting 2026-05-20
medium CVE-2026-6367: Drupal core allows Cross-Site Scripting (XSS) 2026-05-20
medium CVE-2025-13081: Drupal core allows Object Injection 2025-11-18
low CVE-2025-13082: Drupal core allows Content Spoofing 2025-11-18
low CVE-2025-13083: Drupal core allows Exploiting Incorrectly Configured Access Control Security Levels 2025-11-18

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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.