{
"id": "GHSA-xcj9-5m2h-648r",
"aliases": [
"CVE-2026-41148"
],
"details": "### Details\n\nThe state diagram and any other diagram type that routes user-controlled style strings through createCssStyles parser for Mermaid v11.14.0 and earlier captures `classDef` values with an unrestricted regex:\n\n```jison\n// packages/mermaid/src/diagrams/state/parser/stateDiagram.jison:83\n<CLASSDEFID>[^\\n]* { this.popState(); return 'CLASSDEF_STYLEOPTS' }\n```\n\nThe value passes unsanitized through `addStyleClass()` -> `createCssStyles()` -> `style.innerHTML` (mermaidAPI.ts:418). A `}` in the value closes the generated CSS selector, and everything after becomes a new CSS rule on the page.\n\n### PoC\n\n```\nstateDiagram-v2 \n classDef x }*{ background-image: url(\"http://media.giphy.com/media/SggILpMXO7Xt6/giphy.gif\")}\n```\n\nLive demo:\n<https://mermaid.live/edit#pako:eNpFjzFvgzAQhf-KdVNbEcBgMHhtlkqtOnSJKi8ONsYKBmRMlRTx3-skanvTfbp7996t0IxSAYPZC6_2Rmgn7O4rQ00v5nmvWnRG29OKjqI5aTcug9wZK7RiaHH9A4fO-4kliVXSiFibqbvEzWjvnHxo_fI6vR3e6cGXyX2qTcvhcYMItDMSmHeLisAqZ8UVYeUDQhx8p6ziwEIrhTtx4MNVM4nhcxztrywE0h2wVvRzoGWS_z_8rahBKvcckntgmN5OAFvhDIzUNCZZQXCR5nVaZkUEF2BVFpOcEkoxxhUuyRbB980yjStapKHqoKFlhvPtB7BFZEU>\n\n### Patches\n\nThis has been patched in:\n\n- [v11.15.0](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0) (see [e9b0f34d8d82a6260077764ee45e1d7d90957a0f](https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f))\n- [v10.9.6](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6) (see [8fead23c59166b7bab6a39eac81acebee2859102](https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102))\n\n### Workarounds\n\nSetting [`\"securityLevel\": \"sandbox\"`](https://mermaid.js.org/config/schema-docs/config.html#securitylevel) will prevent this, by rendering the mermaid diagram in a sandboxed `<iframe>`.\n\n### Impact\n\n Enables page defacement, user tracking via `url()` callbacks, and DOM attribute exfiltration via CSS `:has()` selectors.",
"summary": "Mermaid: Improper sanitization of `classDefs` in diagrams leads to CSS injection",
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "11.0.0-alpha.1"
},
{
"fixed": "11.15.0"
}
]
}
],
"package": {
"name": "mermaid",
"ecosystem": "npm"
},
"database_specific": {
"last_known_affected_version_range": "<= 11.14.0"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "10.9.6"
}
]
}
],
"package": {
"name": "mermaid",
"ecosystem": "npm"
},
"database_specific": {
"last_known_affected_version_range": "<= 10.9.5"
}
}
],
"modified": "2026-06-08T23:20:59Z",
"severity": [
{
"type": "CVSS_V4",
"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"
}
],
"published": "2026-05-11T19:36:41Z",
"references": [
{
"url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-xcj9-5m2h-648r",
"type": "WEB"
},
{
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41148",
"type": "ADVISORY"
},
{
"url": "https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102",
"type": "WEB"
},
{
"url": "https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f",
"type": "WEB"
},
{
"url": "https://github.com/mermaid-js/mermaid",
"type": "PACKAGE"
},
{
"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",
"type": "WEB"
}
],
"schema_version": "1.4.0",
"database_specific": {
"cwe_ids": [
"CWE-94"
],
"severity": "MODERATE",
"github_reviewed": true,
"nvd_published_at": "2026-05-22T23:16:53Z",
"github_reviewed_at": "2026-05-11T19:36:41Z"
}
}