{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.0.0-alpha.1"
            },
            {
              "fixed": "11.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "mermaid"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.9.0-rc.1"
            },
            {
              "fixed": "10.9.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-54881"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-08-19T20:16:58Z",
    "nvd_published_at": "2025-08-19T17:15:41Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nIn the default configuration of mermaid 11.9.0, user supplied input for sequence diagram labels is passed to `innerHTML` during calculation of element size, causing XSS.\n\n### Details\nSequence diagram node labels with KaTeX delimiters are passed through `calculateMathMLDimensions`. This method passes the full label to `innerHTML` which allows allows malicious users to inject arbitrary HTML and cause XSS when mermaid-js is used in it\u0027s default configuration (with KaTeX support enabled). \n\nThe vulnerability lies here:\n\n```ts\nexport const calculateMathMLDimensions = async (text: string, config: MermaidConfig) =\u003e {\n  text = await renderKatex(text, config);\n  const divElem = document.createElement(\u0027div\u0027);\n  divElem.innerHTML = text; // XSS sink, text has not been sanitized.\n  divElem.id = \u0027katex-temp\u0027;\n  divElem.style.visibility = \u0027hidden\u0027;\n  divElem.style.position = \u0027absolute\u0027;\n  divElem.style.top = \u00270\u0027;\n  const body = document.querySelector(\u0027body\u0027);\n  body?.insertAdjacentElement(\u0027beforeend\u0027, divElem);\n  const dim = { width: divElem.clientWidth, height: divElem.clientHeight };\n  divElem.remove();\n  return dim;\n};\n```\n\nThe `calculateMathMLDimensions` method was introduced in 5c69e5fdb004a6d0a2abe97e23d26e223a059832 two years ago, which was released in [Mermaid 10.9.0](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.0).\n\n### PoC\nRender the following diagram and observe the modified DOM.\n\n```\nsequenceDiagram\n    participant A as Alice\u003cimg src=\"x\" onerror=\"document.write(`xss on ${document.domain}`)\"\u003e$$\\\\text{Alice}$$\n    A-\u003e\u003eJohn: Hello John, how are you?\n    Alice-)John: See you later!\n```\n\nHere is a PoC on mermaid.live: https://mermaid.live/edit#pako:eNpVUMtOwzAQ_BWzyoFKaRTyaFILiio4IK7ckA-1km1iKbaLY6spUf4dJ0AF68uOZ2dm7REqXSNQ6PHDoarwWfDGcMkUudaJGysqceLKkj3hPdl3osJ7IRvSm-qBwcCAaIXGaONRrSsnUdnobITF28PQ954lwXglai25UNNhxWAXBMyXxcGOi-3kL_5k79e73atuFSUv2HWazH1IWn0m3CC5aPf4b3p2WK--BW-4DJCOWzQ3TM0HQmiMqIFa4zAEicZv4iGMsw0D26JEBtS3NR656ywDpiYv869_11r-Ko12TQv0yLveI3eqfcjP111HUNVonrRTFuhdsVgAHWEAmuRxlG7SuEzKMi-yJAnhAjTLIk_EcbFJtuk2y9MphM8lM47KIp--AOZghtU\n\n### Impact\nXSS on all sites that use mermaid and render user supplied diagrams without further sanitization.\n\n### Remediation\nThe value of the `text` argument for the `calculateMathMLDimensions` method needs to be sanitized before getting passed on to `innerHTML`.",
  "id": "GHSA-7rqq-prvp-x9jh",
  "modified": "2025-08-22T22:52:04Z",
  "published": "2025-08-19T20:16:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-7rqq-prvp-x9jh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-54881"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/5c69e5fdb004a6d0a2abe97e23d26e223a059832"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/685516a85ec1df64cefd4fd15f26533be87d458e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mermaid-js/mermaid"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mermaid improperly sanitizes sequence diagram labels leading to XSS"
}