mermaid-js Mermaid up to 11.16.0 Architecture Diagrams prototype pollution

Summaryinfo

A vulnerability described as critical has been identified in mermaid-js Mermaid up to 11.16.0. Affected is an unknown function of the component Architecture Diagrams. Executing a manipulation can lead to prototype pollution. This vulnerability is tracked as CVE-2026-71437. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical was found in mermaid-js Mermaid up to 11.16.0. This vulnerability affects an unknown code block of the component Architecture Diagrams. The manipulation with an unknown input leads to a prototype pollution vulnerability. The CWE definition for the vulnerability is CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. 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.

The advisory is available at github.com. This vulnerability was named CVE-2026-71437 since 08/06/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1059 by the MITRE ATT&CK project.

Upgrading to version 11.16.1 eliminates this vulnerability.

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Productinfo

Vendor

• mermaid-js

Name

• Mermaid

Version

• 11.0
• 11.1
• 11.2
• 11.3
• 11.4
• 11.5
• 11.6
• 11.7
• 11.8
• 11.9
• 11.10
• 11.11
• 11.12
• 11.13
• 11.14
• 11.15
• 11.16.0

Website

• Product: https://github.com/mermaid-js/mermaid/

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