CVE-2026-71438 Details
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.
A prototype pollution vulnerability has been identified in Mermaid, a JavaScript tool for creating diagrams and charts. This issue affects versions 10.9.7 prior to 11.16.1. The vulnerability arises in Mermaid's configuration setters, which merge user-supplied configuration into the internal config using a deep-merge helper vulnerable to prototype pollution. While this vulnerability is generally low risk, as it requires forwarding untrusted data into these configuration points, it could potentially be exploited if not properly managed.
Users can update to Mermaid versions 11.16.1 or 10.9.8, both of which include the necessary fix. Instructions for updating can be found in the Mermaid release notes on GitHub.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No CVSS 3.x data is available for this CVE.
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Aug 7, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1321 | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') | [email protected] |
Affected Products
No affected product data is available for this CVE.
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 7, 2026 | CVE Modified | CISA-ADP |
| Aug 6, 2026 | New CVE Received | [email protected] |