Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection

Description

Under the default configuration, Mermaid state diagram’s classDef allow DOM injection that escapes the SVG, although <script> tags are removed, preventing XSS.

Recommendation

Update the mermaid package to the latest compatible version. Followings are version details:

• Affected version(s): **<= 10.9.5

  >= 11.0.0-alpha.1, <= 11.14.0**

• Patched version(s): **10.9.6

  11.15.0**

References

• GHSA-ghcm-xqfw-q4vr
• mermaid.js.org
• CVE-2026-41149
• CWE-94
• CAPEC-310
• OWASP 2021-A3
• OWASP 2021-A6

Related Issues

• Mermaid: Improper sanitization of `classDefs` in diagrams leads to CSS injection - CVE-2026-41148
• Mermaid: Improper sanitization of configuration leads to CSS injection - CVE-2026-41159
• beautiful-mermaid contains an SVG attribute injection issue that can lead to cross-site scripting (XSS) - CVE-2026-26226
• Marp Core allows XSS by improper neutralization of HTML sanitization - CVE-2024-56510

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Tags:

npm

mermaid