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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mermaid Project | Mermaid | < 10.9.6 |
Related Weaknesses (CWE)
References
- https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afe
- https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd
- https://github.com/mermaid-js/mermaid/releases/tag/[email protected]Release Notes
- https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6Release Notes
- https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4pThird Party Advisory
FAQ
What is CVE-2026-41159?
CVE-2026-41159 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 ...
How severe is CVE-2026-41159?
CVE-2026-41159 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-41159?
Check the references section above for vendor advisories and patch information. Affected products include: Mermaid Project Mermaid.