{"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":"SandboxJS is a JavaScript sandboxing library. Versions prior to 0.8.26 have a sandbox escape vulnerability due to `AsyncFunction` not being isolated in `SandboxFunction`. The 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. However, before version 0.8.26, 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`). In `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. Constructors 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). Version 0.8.26 patches this vulnerability.","published":"2026-01-27T23:32:16.104Z","modified":"2026-08-12T03:51:13.238525025Z","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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:13.238525025Z"}}