Is CVE-2026-8414 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-8414 being exploited in the wild.

How severe is CVE-2026-8414?

Medium severity, with a CVSS score of 4, published 21 May 2026.

Which products and versions are affected?

Concrete CMS 9.0.0RC1 to 9.5.0; concrete5/concrete5 (Packagist) >= 9.0.0RC1, < 9.5.1, ECOSYSTEM:introduced=9.0.0RC1,fixed=9.5.1.

Is there a fix for CVE-2026-8414?

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-2026-8414 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-8414?

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.

CVE-2026-8414: Concrete CMS CSRF in event duplication controller

Q: Is there a fix for CVE-2026-8414?

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.

Q: How is CVE-2026-8414 attacked?

It is attacked over the network, in a web application.

Q: Am I affected by CVE-2026-8414?

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.

CVE-2026-8414 · Severity: medium · CVSS 4 · Published 2026-05-21

Concrete CMS, a popular content management system, is vulnerable to a security flaw that could allow an attacker to trick an administrator into performing unintended actions. Specifically, an attacker could cause the system to duplicate calendar events without the user's consent. While this does not directly expose sensitive data, it can be used to clutter the system or disrupt administrative workflows if a logged-in user visits a malicious website.

Technologies: Concrete CMS, concrete5/concrete5 (Packagist). Vendors: Concrete CMS, Packagist.

Quick answers

Is CVE-2026-8414 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-8414 being exploited in the wild.
How severe is CVE-2026-8414?: Medium severity, with a CVSS score of 4, published 21 May 2026.
Which products and versions are affected?: Concrete CMS 9.0.0RC1 to 9.5.0; concrete5/concrete5 (Packagist) >= 9.0.0RC1, < 9.5.1, ECOSYSTEM:introduced=9.0.0RC1,fixed=9.5.1.
Is there a fix for CVE-2026-8414?: 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-2026-8414 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-8414?: 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 9.0.0RC1 through 9.5.0. The issue is located in the 'concrete/controllers/dialog/event/duplicate' component, which fails to properly validate CSRF tokens or implement 'SameSite' cookie attributes correctly. An attacker can exploit this by crafting a malicious webpage that, when visited by an authenticated administrator, triggers a background request to duplicate calendar events. This vulnerability is classified as CWE-352 and CWE-1275. A fix is available in version 9.5.1.

Affected products

Concrete CMS Concrete CMS 9.0.0RC1 to 9.5.0

Identifiers

CVE-2026-8414
GHSA-98qf-jvwj-2r5f

Timeline

2026-05-21: disclosed: NVD Published Date
2026-05-22: advisory: GitHub Advisory published
2026-06-24: patched: GitHub Advisory updated with patch information

References

https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

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