Quick answers
- Is CVE-2026-8417 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-8417 being exploited in the wild.
- How severe is CVE-2026-8417?
- High severity, with a CVSS score of 4, published 21 May 2026.
- Which products and versions are affected?
- Concrete CMS <= 9.5.0, 9.5.0 and below; concrete5/concrete5 (Packagist) < 9.5.1, ECOSYSTEM:introduced=0,fixed=9.5.1.
- Is there a fix for CVE-2026-8417?
- Yes. concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-8417 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-8417?
- Check whether you run Concrete CMS or concrete5/concrete5 (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later
composer require concrete5/concrete5:^9.5.1
Technical details
A Cross-Site Request Forgery (CSRF) vulnerability exists in Concrete CMS versions 9.5.0 and below. The `do_update()` method in `concrete/controllers/single_page/dashboard/extend/update.php` fails to validate CSRF tokens before executing `upgradeCoreData()` and `upgrade()` on a package's controller. Because the `/dashboard/extend/update/do_update/<pkgHandle>` endpoint is a state-changing GET route without token enforcement, an attacker can use cross-site navigation to force an authenticated administrator (with `canInstallPackages` permissions) to trigger an upgrade for an already installed package. This issue is resolved in version 9.5.1.
Affected products
- Concrete CMS Concrete CMS <= 9.5.0
Identifiers
- CVE-2026-8417
- GHSA-jr5g-qv3g-rxxx
Timeline
- 2026-05-21: disclosed
- 2026-05-21: advisory
- 2026-05-21: patched: Fixed in version 9.5.1