Quick answers
- Is CVE-2026-18119 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18119 being exploited in the wild.
- How severe is CVE-2026-18119?
- Critical severity, with a CVSS score of 9, published 14 September 2026.
- Which products and versions are affected?
- Concrete CMS below 9.5.3.
- Is there a fix for CVE-2026-18119?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-18119 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-18119?
- Check whether you run Concrete CMS 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.
Technical details
This is a stored cross-site scripting (XSS) vulnerability in the Block Design dialog component. The root cause is insufficient sanitization of custom style values before they are inserted into page CSS via a DOM sink. An authenticated editor-level user can craft malicious style input containing JavaScript that will execute when the CSS is rendered in an administrator's browser. The vulnerability requires editor access and user interaction (an admin must view the affected page), but successful exploitation allows arbitrary script execution in the admin session context, enabling privilege escalation and account takeover. Patches are available in version 9.5.3 and later.
Affected products
- Concrete CMS Concrete CMS below 9.5.3
Timeline
- 2026-09-14: disclosed