CVE-2026-41149

Proof-of-concept

stateDiagram-v2
  classDef xss fill:red</style></svg><style>*{x:x;y:y;overflow:visible!important;contain:none!important;transform:none!important;filter:none!important;clip-path:none!important}</style><div style="x:x;y:y;color:red;font:5em/1 monospace;display:grid;place-items:center;z-index:2147483647;width:100vw;height:100vh;position:fixed;top:0;left:0;background:black">HACKED</div><svg><style>a:b
  [*] --> A:::xss

Workarounds

If you can not update to a patched version, setting "securityLevel": "sandbox" will prevent this, by rendering the mermaid diagram in a sandboxed <iframe>.

Credits

Thanks to @zsxsoft from @KeenSecurityLab for reporting this vulnerability.

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

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

Kodem intelligence

• v11.15.0 (see 37ff937f1da2e19f882fd1db01235db4d01f4056)
• v10.9.6 (see 4e2d512bf5bf6f9de1a8f0a48da78dc4d09ac4f3)

1. What is CVE-2026-41149? CVE-2026-41149 is a medium-severity code injection vulnerability in mermaid (npm), affecting versions >= 11.0.0-alpha.1, <= 11.14.0. It is fixed in 11.15.0, 10.9.6. Untrusted input is evaluated as executable code within the application's runtime environment.
2. Which versions of mermaid are affected by CVE-2026-41149? mermaid (npm) versions >= 11.0.0-alpha.1, <= 11.14.0 is affected.
3. Is there a fix for CVE-2026-41149? Yes. CVE-2026-41149 is fixed in 11.15.0, 10.9.6. Upgrade to this version or later.
4. Is CVE-2026-41149 exploitable, and should I be worried? Whether CVE-2026-41149 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-41149 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-41149?
   • Upgrade mermaid to 11.15.0 or later
   • Upgrade mermaid to 10.9.6 or later