CVE-2026-71439

Mermaid before 10.9.8 and 11.16.1 is vulnerable to prototype pollution via configuration setters when untrusted data is passed. Diagram-supplied config is not affected.

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams. From version 11.5.0 until 11.16.1, Mermaid Architecture Diagrams are vulnerable to prototype pollution when a diagram defines a group with an id of __proto__. Because the group id is used directly as an object property key without validation, an attacker who can supply diagram text can pollute Object.prototype, potentially affecting the behavior of the embedding application. This issue is fixed in version 11.16.1.

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams. From version 10.6.0 until 10.9.8 and 11.16.1, Mermaid XY Charts are vulnerable to an infinite loop denial of service in the setXAxisRangeData function when configuring an X-Axis with invalid parameters. Because each loop iteration appends an element to an array, this generally causes a RangeError to appear after a few seconds, but it may instead cause the page or JavaScript process to crash from memory exhaustion, depending on the environment. This issue is fixed in versions 10.9.8 and 11.16.1.

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.8 and 11.16.1, Mermaid is vulnerable to CSS injection via sibling combinator selectors generated from diagram-supplied class or id names. An attacker who can supply diagram text can inject arbitrary CSS into the rendered page, potentially altering the appearance or behavior of unrelated page elements. This issue is fixed in versions 10.9.8 and 11.16.1.

Mermaid, a JavaScript diagramming tool, has a CSS injection vulnerability in its default configuration prior to versions 10.9.6 and 11.15.0. The fontFamily, themeCSS, and altFontFamily options allow injecting CSS that escapes the #mermaid-xxx scoping, enabling page defacement and DOM attribute exfiltration via :has() selectors.

Mermaid before versions 10.9.6 and 11.15.0 is vulnerable to a denial-of-service attack when rendering Gantt charts if the excludes attribute is used to exclude all dates.

In Mermaid up to version 10.9.5 and from 11.0.0-alpha.1 to 11.14.0, there is an HTML injection vulnerability under default configuration. The classDef directive in state diagrams permits DOM injection outside the SVG context, though <script> tags are stripped, preventing XSS.

CSS injection vulnerability in Mermaid up to version 10.9.5 and 11.0.0-alpha.1 through 11.12.0. Improper sanitization in the createCssStyles parser allows CSS injection, leading to page defacement, user tracking, or DOM attribute exfiltration.