GHSA-3RRR-JR9J-H3Q3

Vulnerability from github – Published: 2026-08-06 19:51 – Updated: 2026-08-06 19:51
VLAI
Summary
Mermaid Architecture diagrams are vulnerable to prototype pollution
Details

Rendering an untrusted architecture-beta diagram lets the diagram author write an arbitrary property with the value horizontal or vertical onto Object.prototype. A group id of __proto__ is accepted as a valid parent.

Impact

Any code in the same realm that reads a property of that name from an arbitrary object, or enumerates an object with bare for...in, observes the injected value (which can only be the string horizontal or vertical.

This may mean corrupted option/config defaults, bypassed truthiness checks, causing denial of service or logic corruption in the embedding application.

Because the injected value cannot be an object or function, this is not directly exploitable for remote code execution.

PoC

architecture-beta
      group mermaidPrototypePollutionMarker(cloud)[Marker]
      service a(server)[A] in __proto__
      service b(server)[B] in mermaidPrototypePollutionMarker
      a:R -- L:b

The vulnerable write was introduced in commit cb0a4703bdf01d47508bde1c08aa9a980d70bc20 and first shipped in mermaid@11.5.0. The lines are unchanged in every release since.

Patches

This has been patched by https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf, released in Mermaid v11.16.1

Workarounds

There are no known workarounds. Please update to a patched version.

References

Are there any links users can visit to find out more?

  • https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf
  • https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1
Severity
6.5 (Medium)
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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.5.0"
            },
            {
              "fixed": "11.16.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-71437"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-06T19:51:59Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "Rendering an untrusted `architecture-beta` diagram lets the diagram author write an arbitrary property with the value `horizontal` or `vertical` onto `Object.prototype`. A group id of `__proto__` is accepted as a valid parent.\n\n### Impact\n\nAny code in the same realm that reads a property of that name from an arbitrary object, or enumerates an object with bare `for...in`, observes the injected value (which can only be the string `horizontal` or `vertical`.\n\nThis may mean corrupted option/config defaults, bypassed truthiness checks, causing denial of service or logic corruption in the embedding application.\n\nBecause the injected value cannot be an object or function, this is not directly exploitable for remote code execution.\n\n### PoC\n\n```\narchitecture-beta\n      group mermaidPrototypePollutionMarker(cloud)[Marker]\n      service a(server)[A] in __proto__\n      service b(server)[B] in mermaidPrototypePollutionMarker\n      a:R -- L:b\n```\n\nThe vulnerable write was introduced in commit [cb0a4703bdf01d47508bde1c08aa9a980d70bc20](https://github.com/mermaid-js/mermaid/commit/cb0a4703bdf01d47508bde1c08aa9a980d70bc20) and first shipped in `mermaid@11.5.0`. The lines are unchanged in every release since.\n\n### Patches\n\nThis has been patched by https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf, released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1)\n\n### Workarounds\n\nThere are no known workarounds. Please update to a patched version.\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/99af3fc35ef0a9a9c8c6314521344d67523ddccf\n- https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1",
  "id": "GHSA-3rrr-jr9j-h3q3",
  "modified": "2026-08-06T19:51:59Z",
  "published": "2026-08-06T19:51:59Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-3rrr-jr9j-h3q3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/pull/8022"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mermaid-js/mermaid"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mermaid Architecture diagrams are vulnerable to prototype pollution"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.