Vulnerability-Lookup

GHSA-C4C3-PG64-4M4V

Vulnerability from github – Published: 2026-08-06 19:59 – Updated: 2026-08-06 19:59

Summary

Mermaid configuration APIs allow prototype pollution

Details

Summary

Mermaid's configuration setters (mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig) merge the caller-supplied configuration object into Mermaid's internal config using the assignWithDepth deep-merge helper that is vulnerable to prototype pollution.

Because these APIs are intended to receive trusted configuration supplied by the application integrating Mermaid, Mermaid assesses the practical risk as low. The vulnerability is only reachable if an application forwards attacker-controlled data directly into one of these configuration entry points, which is outside their documented usage.

User-controlled configuration (e.g. configuration in diagram code using %%{init: {}}%% or YAML frontmatter) are already protected from prototype pollution.

Patches

This has been patched in https://github.com/mermaid-js/mermaid/commit/2cd6dcf735533b323507e3e889ffdea870540b43 and released in Mermaid v11.16.1.

A backport has been made for the v10 branch in c34b07a0815842327e70794d69b0c8c5a1e2a956 and was released in Mermaid v10.9.8

Impact

Mermaid believes it's unlikely that anybody is impacted, as these functions are configuration entry points expected to receive trusted, developer-controlled values as they can modify other security-relevant configuration.

Workarounds

Don't pass user-controlled data to the mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig functions. Instead, users can use %%{init: {}}%% or YAML frontmatter in diagrams.

Reporters

liyi.zhou@sydney.edu.au (Liyi), https://lzhou1110.github.io/
ziyue0530@gmail.com (Ziyue), https://zyy0530.github.io/
cshe0476@uni.sydney.edu.au (Strick), https://str1ckl4nd.github.io/
chng0012@uni.sydney.edu.au (Maurice), http://maurice.busystar.org/
cyu210608@gmail.com (Chenchen), https://7thparkk.github.io/

Severity

2.4 (Low)


                  
                    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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.0.0-alpha.1"
            },
            {
              "fixed": "11.16.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "10.9.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-71438"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-06T19:59:10Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Summary\n\nMermaid\u0027s configuration setters (`mermaid.initialize`, `mermaidAPI.setConfig`, and `mermaidAPI.updateSiteConfig`) merge the caller-supplied configuration object into Mermaid\u0027s internal config using the `assignWithDepth` deep-merge helper that is vulnerable to prototype pollution.\n\nBecause these APIs are intended to receive **trusted** configuration supplied by the application integrating Mermaid, Mermaid assesses the practical risk as **low**. The vulnerability is only reachable if an application forwards attacker-controlled data directly into one of these configuration entry points, which is outside their documented usage.\n\nUser-controlled configuration (e.g. configuration in diagram code using `%%{init: {}}%%` or YAML frontmatter) are already protected from prototype pollution.\n\n### Patches\n\nThis has been patched in https://github.com/mermaid-js/mermaid/commit/2cd6dcf735533b323507e3e889ffdea870540b43 and released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1).\n\nA backport has been made for the v10 branch in c34b07a0815842327e70794d69b0c8c5a1e2a956 and was released in [Mermaid v10.9.8](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8)\n\n### Impact\n\nMermaid believes it\u0027s unlikely that anybody is impacted, as these functions are configuration entry points expected to receive trusted, developer-controlled values as they can modify other security-relevant configuration.\n\n### Workarounds\n\nDon\u0027t pass user-controlled data to the `mermaid.initialize`, `mermaidAPI.setConfig`, and `mermaidAPI.updateSiteConfig` functions. Instead, users can use `%%{init: {}}%%` or YAML frontmatter in diagrams.\n\n### Reporters\n\n- liyi.zhou@sydney.edu.au (Liyi), https://lzhou1110.github.io/\n- ziyue0530@gmail.com (Ziyue), https://zyy0530.github.io/\n- cshe0476@uni.sydney.edu.au (Strick), https://str1ckl4nd.github.io/\n- chng0012@uni.sydney.edu.au (Maurice), http://maurice.busystar.org/\n- cyu210608@gmail.com (Chenchen), https://7thparkk.github.io/",
  "id": "GHSA-c4c3-pg64-4m4v",
  "modified": "2026-08-06T19:59:10Z",
  "published": "2026-08-06T19:59:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-c4c3-pg64-4m4v"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/pull/8022"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/2cd6dcf735533b323507e3e889ffdea870540b43"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/c34b07a0815842327e70794d69b0c8c5a1e2a956"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mermaid-js/mermaid"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mermaid configuration APIs allow prototype pollution"
}

CVE-2026-71438 (GCVE-0-2026-71438)

Vulnerability from cvelistv5 – Published: 2026-08-06 19:59 – Updated: 2026-08-06 19:59

Title

Mermaid configuration APIs allow prototype pollution

Summary

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.

Severity

2.4 (Low)


                        
                          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

CWE

CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M

References

6 references

URL	Tags
https://github.com/mermaid-js/mermaid/security/ad…	x_refsource_CONFIRM
https://github.com/mermaid-js/mermaid/pull/8022	x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/2cd6…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/c34b…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/ta…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/ta…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mermaid-js	mermaid	Affected: < 10.9.8 Affected: >= 11.0.0-alpha.1, < 11.16.1

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JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "mermaid",
          "vendor": "mermaid-js",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 10.9.8"
            },
            {
              "status": "affected",
              "version": "\u003e= 11.0.0-alpha.1, \u003c 11.16.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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\u0027s configuration setters (mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig) merge caller-supplied configuration into Mermaid\u0027s 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."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "LOCAL",
            "baseScore": 2.4,
            "baseSeverity": "LOW",
            "privilegesRequired": "HIGH",
            "subAvailabilityImpact": "HIGH",
            "subConfidentialityImpact": "HIGH",
            "subIntegrityImpact": "HIGH",
            "userInteraction": "ACTIVE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1321",
              "description": "CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-06T19:59:07.450Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-c4c3-pg64-4m4v",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-c4c3-pg64-4m4v"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/pull/8022",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/pull/8022"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/commit/2cd6dcf735533b323507e3e889ffdea870540b43",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/commit/2cd6dcf735533b323507e3e889ffdea870540b43"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/commit/c34b07a0815842327e70794d69b0c8c5a1e2a956",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/commit/c34b07a0815842327e70794d69b0c8c5a1e2a956"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"
        }
      ],
      "source": {
        "advisory": "GHSA-c4c3-pg64-4m4v",
        "discovery": "UNKNOWN"
      },
      "title": "Mermaid configuration APIs allow prototype pollution"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-71438",
    "datePublished": "2026-08-06T19:59:07.450Z",
    "dateReserved": "2026-08-06T16:28:51.183Z",
    "dateUpdated": "2026-08-06T19:59:07.450Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-C4C3-PG64-4M4V

Summary

Patches

Impact

Workarounds

Reporters

CVE-2026-71438 (GCVE-0-2026-71438)

Tags

Sightings

Nomenclature