---
id: CVE-2026-18119
title: >-
  Concrete CMS below 9.5.3 did not sanitize custom style values in the Block
  Design dialog before writing them into page CSS via a DOM sink, permitting
  stored cross-site scripting
summary: >-
  Concrete CMS below 9.5.3 did not sanitize custom style values in the Block
  Design dialog before writing them into page CSS via a DOM sink, permitting
  stored cross-site scripting. An editor-level user could execute script in an
  administra…
severity: critical
cvss: 9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H'
cwe:
  - CWE-79
vendor: concretecms
product: concrete_cms
affected:
  - concrete_cms < 9.5.3
patched:
  - concrete_cms 9.5.3
published: '2026-09-14'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T19:23:08.313'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18119'
references:
  - url: >-
      https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
    label: ff5b8ace-8b95-4078-9743-eac1ca5451de
tags:
  - nvd
  - cve.org
  - score-dispute
epss: 0.00312
epssPercentile: 0.21365
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-14T20:06:50.657332Z'
scores:
  nvd: 9
  cna: 7
ingestedAt: '2026-09-14T20:14:21.144Z'
---

## Overview

Concrete CMS below 9.5.3 did not sanitize custom style values in the Block Design dialog before writing them into page CSS via a DOM sink, permitting stored cross-site scripting. An editor-level user could execute script in an administrator's session and escalate privileges. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Nguyen Manh Thuan for reporting.

## Affected

- `concrete_cms < 9.5.3`

## Remediation

Upgrade past the affected range:

- `concrete_cms 9.5.3`