---
id: CVE-2026-71437
title: >-
  Mermaid is a JavaScript tool that uses Markdown-inspired text to create and
  modify diagrams and charts
summary: >-
  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…
severity: medium
cwe:
  - CWE-1321
vendor: mermaid
product: mermaid
affected:
  - 'mermaid >= 11.5.0, < 11.16.1'
patched:
  - mermaid 11.16.1
published: '2026-08-06'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T20:53:06.753'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-71437'
references:
  - url: >-
      https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf
    label: security-advisories@github.com
  - url: 'https://github.com/mermaid-js/mermaid/pull/8022'
    label: security-advisories@github.com
  - url: 'https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1'
    label: security-advisories@github.com
  - url: >-
      https://github.com/mermaid-js/mermaid/security/advisories/GHSA-3rrr-jr9j-h3q3
    label: security-advisories@github.com
  - url: >-
      https://github.com/mermaid-js/mermaid/security/advisories/GHSA-3rrr-jr9j-h3q3
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-3rrr-jr9j-h3q3'
tags:
  - nvd
  - ghsa
  - npm
epss: 0.00503
epssPercentile: 0.404
aliases:
  - GHSA-3rrr-jr9j-h3q3
ecosystem: npm
ingestedAt: '2026-08-06T20:03:56.419Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-71437)

Affected packages:

- `mermaid >= 11.5.0, < 11.16.1`

Patched in:

- `mermaid 11.16.1`

Source: https://github.com/advisories/GHSA-3rrr-jr9j-h3q3