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CVE-2026-18119— Concrete CMS below 9.5.3 is vulnerable to Stored XSS via unsanitized inline block custom style values

Quick assessment

Affected
Concrete CMS Concrete CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Concrete CMS 9.5.3 之前的版本未在“区块设计”对话框中对自定义样式值进行清理，就直接通过 DOM 汇点（DOM sink）将其写入页面 CSS，从而允许发生存储型跨站脚本攻击（Stored XSS）。具有编辑器权限的用户可以在管理员的会话中执行脚本，进而提升权限。Concrete CMS 安全团队为该漏洞分配的 CVSS v4.0 得分为 7.0，向量表达式为：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。感谢 Ng

CVSS 7.0 · High

Possible ATT&CK Techniques 1 AI

T1059.007 · JavaScript
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I. Basic Information for CVE-2026-18119

Vulnerability Information
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Vulnerability Title
Concrete CMS below 9.5.3 is vulnerable to Stored XSS via unsanitized inline block custom style values
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 5.0.0 ~ 9.5.2 -

II. Public POCs for CVE-2026-18119

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III. Intelligence Information for CVE-2026-18119

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Vendor Pages for CVE-2026-18119 (1)

Same Patch Batch · Concrete CMS · 2026-09-14 · 5 CVEs total

CVE-2026-18117 7.3 HIGH Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Custom Page Alias Name
CVE-2026-81901 7.2 HIGH Concrete CMS 9.2.0 to 9.5.2 is vulnerable to stored XSS due to missing authorization in th
CVE-2026-81902 7.1 HIGH Concrete CMS 9.0.0 to 9.5.2 is vulnerable to CSRF on Orphan Block Cleanup
CVE-2026-81903 7.0 HIGH Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Stored XSS via Page Container icon

IV. Related Vulnerabilities

Same product: Concrete CMS
Same vendor: Concrete CMS
Same weakness: CWE-79

V. Comments for CVE-2026-18119

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