CVE-2026-8353 Concrete CMS version 9.0 to 9.5.0 is vulnerable to Stored XSS via page name in atomik theme
A rogue editor can inject JavaScript via page names in the Atomik theme, leading to session hijacking and privilege escalation for other users.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-8353?
CVE-2026-8353 is a low-severity cross-site scripting vulnerability in Concretecms Concrete Cms, published on 22 May 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Concrete CMS version 9.0 to 9.5.0 is vulnerable to Stored XSS via page name in the Atomik theme. A rogue editor can inject arbitrary JavaScript that executes in the context of any authenticated user visiting the affected account pages. This can lead to session hijacking, credential theft, malicious actions performed on behalf of users, and potential privilege escalation. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) for reporting.
Weakness: CWE-79
Which versions are affected by CVE-2026-8353?
2 open source packages ship an affected version, including concrete5/concrete5. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
concrete5/concrete5 Packagist | From 9.0.0RC.1 | 9.5.1 |
concrete5/concrete5 Packagist | From 9.0.0RC.1 | 9.5.1 |
Products include Concretecms Concrete Cms.
How do I fix CVE-2026-8353?
Upgrade concrete5/concrete5 to 9.5.1 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-8353 being exploited?
There is no known exploitation of CVE-2026-8353 in the wild and no public exploit code.
Other vulnerabilities in Concretecms Concrete Cms
- CVE-2023-48648 Concrete CMS allows unauthorized access because directories can be created with insecure permissions
- CVE-2022-21829 Code injection in concrete CMS
- CVE-2021-22958 Server-Side Request Forgery vulnerability in concrete5
- CVE-2021-40098 Path traversal in n/a
- CVE-2026-8134 Concrete CMS Vulnerable to Relative Path Traversal
Sources
Also known as GHSA-q9fm-mpg8-8jqm.