CVE-2026-71437 MEDIUM

CVE-2026-71437: Mermaid Architecture diagrams are vulnerable to prototype pollution

Vendor Mermaid-Js
Product mermaid
Weakness CWE-1321
Published August 6, 2026
Last update August 7, 2026

CVSS base score

6.5/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:H/SI:H/SA:H

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

August 6, 2026 CVE published
August 7, 2026 Record updated