CVE-2026-41149: Mermaid-Js Mermaid

Medium severity, CVSS 5.3. EPSS: 0.5% chance of exploitation in the next 30 days.

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and earlier, as well as 11.0.0-alpha.1 through 11.14.0, are vulnerable to HTML injection under the default configuration. Specifically, the classDef directive in Mermaid state diagrams permits DOM injection that escapes the SVG context. However, <script> tags are stripped, which prevents cross-site scripting (XSS). This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting "securityLevel": "sandbox", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>.

Affected products

• Mermaid-Js Mermaid: from 11.0.0-alpha.1, before 11.15.0 (fixed in 11.15.0); before 10.9.6 (fixed in 10.9.6)

Published 2026-05-22. Last modified 2026-07-23.