CVE-2026-71439: Mermaid Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-rhh3-jpg6-66xh
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CWE-606 CWE-1322
Published
Advisory Summary

CVE-2026-71439 is a MODERATE denial of service vulnerability (CWE-606: Unchecked Input for Loop Condition) affecting Mermaid libraries in the npm ecosystem. The issue involves mermaid radar diagrams are vulnerable to dos. Remediation is available by upgrading affected packages to version 11.16.1.

CVE-2026-71439 at a Glance

CVE Identifier CVE-2026-71439
GHSA Identifier GHSA-rhh3-jpg6-66xh
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-606: Unchecked Input for Loop Condition
Affected Product Mermaid
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-71439

To remediate this vulnerability, upgrade all affected Mermaid dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

mermaid fixed: 11.16.1 
npm install mermaid@11.16.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls mermaid

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-71439, inspect your project dependencies using npm:

npm ls mermaid

Analyze the terminal output to locate any version of Mermaid in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 11.16.1), your application is affected.

Note: The npm ls mermaid command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-606: Unchecked Input for Loop Condition, where the product does not properly check inputs that are used for loop conditions, potentially leading to a denial of service or other consequences because of excessive looping. In Mermaid, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Mermaid radar diagrams allow arbitrary large values for `ticks`, which can cause high CPU usage, freezing the webpage/JavaScript process for long periods of time, until the process is eventually killed due to OOM/running out of memory. #### Proof-of-concept ```txt radar-beta axis a, b curve c {1, 1} ticks 1000000000 ``` ### Patches _Has the problem been patched? What versions should users upgrade to?_ This problem has been patched by https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e, which was released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1) ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ There are no known workarounds without updating to a patched version of mermaid. ### References _Are there any links users can visit to find out more?_ - https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e - https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1

CVE-2026-71439 Affected Mermaid Versions

1 component(s)
Fixed Versions:
11.16.1
Product / Package Ecosystem Affected Versions Fixed Version
mermaid
npm/mermaid
npm
≥ 11.6.0
< 11.16.1
11.16.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/mermaid-js/mermaid/security/advisories/GHSA-rhh3-jpg6-66xh
Mermaid Source Repository REPOSITORY
https://github.com/mermaid-js/mermaid/pull/8022
Security Fix Commit FIX COMMIT
https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e
Mermaid Source Repository REPOSITORY
https://github.com/mermaid-js/mermaid
Mermaid Release RELEASE
https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1

Frequently Asked Questions

What is CVE-2026-71439?
CVE-2026-71439 is a security vulnerability in Mermaid involving Mermaid radar diagrams are vulnerable to DoS under CWE-606: Unchecked Input for Loop Condition.
Which Mermaid versions are affected?
Affected versions include releases prior to 11.16.1 across affected packages: mermaid.
What version fixes CVE-2026-71439?
Upgrading to 11.16.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mermaid affected?
Yes, mermaid is affected in releases prior to 11.16.1. Upgrade your dependency to 11.16.1 or later.
What CWE is associated with CVE-2026-71439?
CVE-2026-71439 is classified under CWE-606: Unchecked Input for Loop Condition (The product does not properly check inputs that are used for loop conditions, potentially leading to a denial of service or other consequences because of excessive looping.).
How can I check npm dependencies for CVE-2026-71439?
Run the dependency tree command: 'npm ls mermaid'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rhh3-jpg6-66xh",
  "modified" : "2026-08-06T20:01:07Z",
  "published" : "2026-08-06T20:01:07Z",
  "aliases" : [ "CVE-2026-71439" ],
  "summary" : "Mermaid radar diagrams are vulnerable to DoS",
  "details" : "### Impact\n\nMermaid radar diagrams allow arbitrary large values for `ticks`, which can cause high CPU usage, freezing the webpage/JavaScript process for long periods of time, until the process is eventually killed due to OOM/running out of memory.\n\n#### Proof-of-concept\n\n```txt\nradar-beta\n  axis a, b\n  curve c {1, 1}\n  ticks 1000000000\n```\n\n### Patches\n\n_Has the problem been patched? What versions should users upgrade to?_\n\nThis problem has been patched by https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e, which was released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1)\n\n### Workarounds\n\n_Is there a way for users to fix or remediate the vulnerability without upgrading?_\n\nThere are no known workarounds without updating to a patched version of mermaid.\n\n### References\n\n_Are there any links users can visit to find out more?_\n\n- https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e\n- https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "mermaid"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "11.6.0"
      }, {
        "fixed" : "11.16.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-rhh3-jpg6-66xh"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mermaid-js/mermaid/pull/8022"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mermaid-js/mermaid/commit/59b22fad2b3bb04f87a476c84a8a2b24679e607e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mermaid-js/mermaid"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1322", "CWE-606" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-06T20:01:07Z",
    "nvd_published_at" : null
  }
}