craftcms/cms security advisory

CVE-2026-56381: Craft CMS Vulnerable to Stored XSS via User Group Name in User Permissions Page

CVE-2026-56381 is a low-severity stored XSS vulnerability in the PHP package craftcms/cms (CVSS 4.8), published 21 June 2026. The advisory does not name a fixed version. Exploiting it needs an admin-level account.

low 4.8 published 2026-06-21 · updated 2026-10-25

Affected versions: >= 5.0.0-RC1, <= 5.8.21
Fixed in: not stated
Newest release: 5.12.0
Severity: Low · CVSS 4.8
Type: Stored cross-site scripting (XSS)
CWE-79
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-2026-56381

Access: A high-privilege account in the app, such as an admin.
Interaction: A user also has to do something, such as open a link or a page the attacker prepared.

CVSS vector (scored by VulnCheck): CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A: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-2026-56381 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.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "craftcms/cms": "^5.12.0" 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-2026-56381.
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 stored XSS issues while the upgrade waits. None of it replaces the fix.

Escape output in your own templates and add a Content-Security-Policy that blocks inline scripts.
Limit who can save the content the advisory names (for example rich text, SVG or form fields).
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-56381 advisory

Craft CMS from version 5.0.0-RC1 contains a stored cross-site scripting vulnerability in the User Permissions page where user group names are rendered without proper HTML escaping. Attackers with admin access can inject arbitrary JavaScript via the user group name field that executes when other users view or edit permissions.

Description from the CVE record, published by VulnCheck (the CVE Numbering Authority), via the NVD entry for CVE-2026-56381. Advisory title: “Craft CMS Vulnerable to Stored XSS via User Group Name in User Permissions Page”.

References

GitHub advisory GHSA-g3hp-vvqf-8vw6 github.com
Vulncheck security advisory www.vulncheck.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

Need help patching or upgrading? Laskyr does PHP and Laravel security fixes and upgrades. Tell us what you run and we reply with a plan and a price.

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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.