Is CVE-2026-8353 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-8353 being exploited in the wild.

How severe is CVE-2026-8353?

Medium severity, with a CVSS score of 4.8, published 22 May 2026.

Which products and versions are affected?

Concrete CMS 9.0 to 9.5.0, 9.0.0RC.1 to 9.5.0; concrete5/concrete5 (Packagist) >= 9.0.0RC.1, < 9.5.1, ECOSYSTEM:introduced=9.0.0RC.1,fixed=9.5.1.

Is there a fix for CVE-2026-8353?

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-2026-8353 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2026-8353?

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-2026-8353: Concrete CMS Stored XSS via page name in Atomik theme

Q: Is there a fix for CVE-2026-8353?

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-2026-8353 attacked?

It is attacked over the network, in a network appliance.

Q: Am I affected by CVE-2026-8353?

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-2026-8353 · Severity: medium · CVSS 4.8 · Published 2026-05-22

Concrete CMS, a platform used for building and managing websites, contains a security flaw in its 'Atomik' theme. A user with editing privileges can insert malicious scripts into a page name, which will then execute when other logged-in users visit specific account pages. This could allow an attacker to hijack user sessions, steal login credentials, or perform unauthorized actions on behalf of other users.

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

Quick answers

Is CVE-2026-8353 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-8353 being exploited in the wild.
How severe is CVE-2026-8353?: Medium severity, with a CVSS score of 4.8, published 22 May 2026.
Which products and versions are affected?: Concrete CMS 9.0 to 9.5.0, 9.0.0RC.1 to 9.5.0; concrete5/concrete5 (Packagist) >= 9.0.0RC.1, < 9.5.1, ECOSYSTEM:introduced=9.0.0RC.1,fixed=9.5.1.
Is there a fix for CVE-2026-8353?: 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-2026-8353 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-8353?: 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 Stored Cross-Site Scripting (XSS) vulnerability exists in Concrete CMS versions 9.0 through 9.5.0 within the Atomik theme. The flaw is rooted in the improper neutralization of input during web page generation (CWE-79) specifically involving page names. An authenticated attacker with 'editor' or higher privileges can inject a malicious JavaScript payload into a page name. This script executes in the browser context of any authenticated user who navigates to the affected account pages. Successful exploitation can lead to session hijacking, credential theft, and privilege escalation. The issue is addressed in Concrete CMS version 9.5.1.

Affected products

Concrete CMS Concrete CMS 9.0 to 9.5.0

Identifiers

CVE-2026-8353
GHSA-q9fm-mpg8-8jqm

Timeline

2026-05-22: disclosed
2026-05-22: advisory
2026-05-22: patched: Fixed in version 9.5.1

References

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