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CVE-2026-71438— Mermaid configuration APIs allow prototype pollution

Quick assessment

Affected
mermaid-js mermaid
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

mermaid-js Mermaid是mermaid-js社区开源的一款通过文本定义图表的图表绘制工具。 mermaid-js mermaid 10.9.8之前版本和11.16.1之前版本存在输入验证错误漏洞，该漏洞源于配置setters使用assignWithDepth深度合并时容易受到原型污染攻击。

CVSS 2.4 · Low EPSS 0.35% · P27

Affected Version Matrix 2

VendorProduct Version RangeStatus
mermaid-js mermaid < 10.9.8 affected
>= 11.0.0-alpha.1, < 11.16.1 affected
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I. Basic Information for CVE-2026-71438

Vulnerability Information
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Vulnerability Title
Mermaid configuration APIs allow prototype pollution
Source: CVE Program / CVE List V5
Vulnerability Description
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's configuration setters (mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig) merge caller-supplied configuration into Mermaid's internal config using the assignWithDepth deep-merge helper, which is vulnerable to prototype pollution. This is only exploitable if an application forwards untrusted data directly into one of these configuration entry points, which is outside their documented usage; diagram-supplied configuration (e.g. %%{init: {}}%% or YAML frontmatter) is not affected. This issue is fixed in versions 10.9.8 and 11.16.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:A/VC:N/VI:L/VA:L/SC:H/SI:H/SA:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1321
Source: CVE Program / CVE List V5
Vulnerability Title
mermaid-js mermaid 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
mermaid-js Mermaid是mermaid-js社区开源的一款通过文本定义图表的图表绘制工具。 mermaid-js mermaid 10.9.8之前版本和11.16.1之前版本存在输入验证错误漏洞，该漏洞源于配置setters使用assignWithDepth深度合并时容易受到原型污染攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mermaid-js mermaid < 10.9.8 -

II. Public POCs for CVE-2026-71438

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III. Intelligence Information for CVE-2026-71438

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Patches & Fixes for CVE-2026-71438 (1)

Vendor Advisories for CVE-2026-71438 (1)

Vendor Pages for CVE-2026-71438 (1)

Other References for CVE-2026-71438 (1)

Same Patch Batch · mermaid-js · 2026-08-06 · 5 CVEs total

CVE-2026-71437 6.5 MEDIUM Mermaid Architecture diagrams are vulnerable to prototype pollution
CVE-2026-71439 5.3 MEDIUM Mermaid radar diagrams are vulnerable to DoS
CVE-2026-71436 5.3 MEDIUM Mermaid XY Charts are vulnerable to an infinite loop DoS
CVE-2026-50159 5.3 MEDIUM Mermaid allows CSS injection applying to sibling elements of the diagram

IV. Related Vulnerabilities

Same product: mermaid
Same vendor: mermaid-js
Same weakness: CWE-1321

V. Comments for CVE-2026-71438

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