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CVE-2026-41159— Mermaid: Improper sanitization of configuration leads to CSS injection

Quick assessment

Affected
mermaid-js mermaid
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.

Mermaid是mermaid-js开源的一个应用软件。使用文本和代码创建图表和可视化。 Mermaid 10.9.6之前版本和11.15.0之前版本存在代码注入漏洞，该漏洞源于默认配置允许通过fontFamily、themeCSS和altFontFamily配置选项注入应用于Mermaid图表外部的CSS。注入的CSS利用stylis的&范围引用处理，通过:not(&)转义#mermaid-xxx自动范围，将样式应用于所有页面元素。全局at规则也可被注入，导致页面破坏和通过CSS :has()选择器进行

AI Predicted 5.3 Difficulty: Easy EPSS 0.55% · P44

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 2

VendorProduct Version RangeStatus
mermaid-js mermaid >= 11.0.0-alpha.1, < 11.15.0 affected
< 10.9.6 affected
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I. Basic Information for CVE-2026-41159

Vulnerability Information
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Vulnerability Title
Mermaid: Improper sanitization of configuration leads to CSS injection
Source: CVE Program / CVE List V5
Vulnerability Description
Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6 and 11.15.0, Mermaid's default configuration allows injecting CSS that applies outside of the Mermaid diagram via the fontFamily, themeCSS, and altFontFamily configuration options. The injected CSS exploits stylis's & (scope reference) handling. :not(&) escapes the #mermaid-xxx automatic scoping, applying styles to all page elements. Global at-rules (@font-face, @keyframes, @counter-style) are also injectable as stylis hoists them to top level. This allows page defacement and DOM attribute exfiltration via CSS :has() selectors. This vulnerability is fixed in 10.9.6 and 11.15.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Vulnerability Title
Mermaid 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mermaid是mermaid-js开源的一个应用软件。使用文本和代码创建图表和可视化。 Mermaid 10.9.6之前版本和11.15.0之前版本存在代码注入漏洞，该漏洞源于默认配置允许通过fontFamily、themeCSS和altFontFamily配置选项注入应用于Mermaid图表外部的CSS。注入的CSS利用stylis的&范围引用处理，通过:not(&)转义#mermaid-xxx自动范围，将样式应用于所有页面元素。全局at规则也可被注入，导致页面破坏和通过CSS :has()选择器进行
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mermaid-js mermaid >= 11.0.0-alpha.1, < 11.15.0 -

II. Public POCs for CVE-2026-41159

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III. Intelligence Information for CVE-2026-41159

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Patches & Fixes for CVE-2026-41159 (3)

Vendor Advisories for CVE-2026-41159 (1)

Vendor Pages for CVE-2026-41159 (2)

IV. Related Vulnerabilities

Same product: mermaid
Same vendor: mermaid-js
Same weakness: CWE-94

V. Comments for CVE-2026-41159

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