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GHSA-GHCM-XQFW-Q4VR

Vulnerability from github – Published: 2026-05-11 19:36 – Updated: 2026-06-08 23:21

Summary

Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection

Details

Impact

Under the default configuration, Mermaid state diagram's classDef allow DOM injection that escapes the SVG, although <script> tags are removed, preventing XSS.

Proof-of-concept

stateDiagram-v2
  classDef xss fill:red</style></svg><style>*{x:x;y:y;overflow:visible!important;contain:none!important;transform:none!important;filter:none!important;clip-path:none!important}</style><div style="x:x;y:y;color:red;font:5em/1 monospace;display:grid;place-items:center;z-index:2147483647;width:100vw;height:100vh;position:fixed;top:0;left:0;background:black">HACKED</div><svg><style>a:b
  [*] --> A:::xss

Patches

Workarounds

If you can not update to a patched version, setting "securityLevel": "sandbox" will prevent this, by rendering the mermaid diagram in a sandboxed <iframe>.

Credits

Thanks to @zsxsoft from @KeenSecurityLab for reporting this vulnerability.

Severity

5.3 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 11.14.0"
      },
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.0.0-alpha.1"
            },
            {
              "fixed": "11.15.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 10.9.5"
      },
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "10.9.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41149"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-11T19:36:46Z",
    "nvd_published_at": "2026-05-22T23:16:53Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nUnder the default configuration, Mermaid state diagram\u0027s `classDef` allow DOM injection that escapes the SVG, although `\u003cscript\u003e` tags are removed, preventing XSS.\n\n#### Proof-of-concept\n\n```\nstateDiagram-v2\n  classDef xss fill:red\u003c/style\u003e\u003c/svg\u003e\u003cstyle\u003e*{x:x;y:y;overflow:visible!important;contain:none!important;transform:none!important;filter:none!important;clip-path:none!important}\u003c/style\u003e\u003cdiv style=\"x:x;y:y;color:red;font:5em/1 monospace;display:grid;place-items:center;z-index:2147483647;width:100vw;height:100vh;position:fixed;top:0;left:0;background:black\"\u003eHACKED\u003c/div\u003e\u003csvg\u003e\u003cstyle\u003ea:b\n  [*] --\u003e A:::xss\n```\n\n### Patches\n\n- [v11.15.0](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0) (see [37ff937f1da2e19f882fd1db01235db4d01f4056](https://github.com/mermaid-js/mermaid/commit/37ff937f1da2e19f882fd1db01235db4d01f4056))\n- [v10.9.6](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6) (see [4e2d512bf5bf6f9de1a8f0a48da78dc4d09ac4f3](https://github.com/mermaid-js/mermaid/commit/4e2d512bf5bf6f9de1a8f0a48da78dc4d09ac4f3))\n\n### Workarounds\n\nIf you can not update to a patched version, setting [`\"securityLevel\": \"sandbox\"`](https://mermaid.js.org/config/schema-docs/config.html#securitylevel)  will prevent this, by rendering the mermaid diagram in a sandboxed `\u003ciframe\u003e`.\n\n### Credits\n\nThanks to @zsxsoft from @KeenSecurityLab for reporting this vulnerability.",
  "id": "GHSA-ghcm-xqfw-q4vr",
  "modified": "2026-06-08T23:21:04Z",
  "published": "2026-05-11T19:36:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-ghcm-xqfw-q4vr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41149"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/37ff937f1da2e19f882fd1db01235db4d01f4056"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/4e2d512bf5bf6f9de1a8f0a48da78dc4d09ac4f3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mermaid-js/mermaid"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6"
    },
    {
      "type": "WEB",
      "url": "https://mermaid.js.org/config/schema-docs/config.html#securitylevel"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection"
}

CVE-2026-41149 (GCVE-0-2026-41149)

Vulnerability from cvelistv5 – Published: 2026-05-22 22:34 – Updated: 2026-05-23 03:22

Title

Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection

Summary

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and earlier, as well as 11.0.0-alpha.1 through 11.14.0, are vulnerable to HTML injection under the default configuration. Specifically, the classDef directive in Mermaid state diagrams permits DOM injection that escapes the SVG context. However, <script> tags are stripped, which prevents cross-site scripting (XSS). This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting "securityLevel": "sandbox", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>.

Severity

5.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-23 03:21 UTC

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/mermaid-js/mermaid/security/ad…	x_refsource_CONFIRM
https://github.com/mermaid-js/mermaid/commit/37ff…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/4e2d…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mermaid-js	mermaid	Affected: >= 11.0.0-alpha.1, < 11.15.0 Affected: < 10.9.6

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-41149",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-23T03:21:57.740211Z",
                "version": "2.0.3"
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            "tags": [
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            "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-ghcm-xqfw-q4vr"
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        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "mermaid",
          "vendor": "mermaid-js",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 11.0.0-alpha.1, \u003c 11.15.0"
            },
            {
              "status": "affected",
              "version": "\u003c 10.9.6"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and earlier, as well as 11.0.0-alpha.1 through 11.14.0, are vulnerable to HTML injection under the default configuration. Specifically, the classDef directive in Mermaid state diagrams permits DOM injection that escapes the SVG context. However, \u003cscript\u003e tags are stripped, which prevents cross-site scripting (XSS). This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting \"securityLevel\": \"sandbox\", which prevents the issue by rendering the mermaid diagram in a sandboxed \u003ciframe\u003e."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "LOW",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "PASSIVE",
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            "vulnConfidentialityImpact": "NONE",
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          }
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      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-94",
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        },
        {
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        "advisory": "GHSA-ghcm-xqfw-q4vr",
        "discovery": "UNKNOWN"
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      "title": "Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection"
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    "datePublished": "2026-05-22T22:34:36.944Z",
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}

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.

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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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