Mermaid allows CSS injection applying to sibling elements of the diagram

Description

Mermaid does not fully restrict CSS to the rendered SVG subtree. Although selectors are prefixed with #mermaid-X, sibling (~ and +) combinators can still escape the Mermaid container and inject styles to DOM elements adjacent to the diagram <svg>.

Recommendation

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

• Affected version(s): **< 10.9.8

  >= 11.0.0-alpha.1, < 11.16.1**

• Patched version(s): **10.9.8

  11.16.1**

References

• GHSA-6x64-9x62-f2gx
• CVE-2026-50159
• 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
• CryptPad has a Sanitizer Bypass in Diffmarked.js that Allows Arbitrary HTML Injection and Potential XSS - CVE-2026-26028
• tarteaucitron.js allows UI manipulation via unrestricted CSS injection - CVE-2025-31138

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Tags:

npm

mermaid