GHSA-mhwj-73qx-jqxm is a high-severity (CVSS 7.5) vulnerability in @theecryptochad/merge-guard. O3 Security confirms whether GHSA-mhwj-73qx-jqxm is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@theecryptochad/merge-guard has Prototype Pollution in its deepMerge() function
Real-World Exposure
@theecryptochad/merge-guardReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Summary
@theecryptochad/merge-guard versions prior to 1.0.1 are vulnerable to Prototype Pollution via the deepMerge() function. An attacker who controls the source object can inject __proto__ keys that mutate Object.prototype, affecting all objects in the Node.js runtime.
Details
The deepMerge() function recursively merges two objects without sanitizing reserved property keys (__proto__, constructor, prototype). When a source object contains a __proto__ key, its value is assigned to target.__proto__, which JavaScript engines interpret as a write to Object.prototype.
Proof of Concept
const { deepMerge } = require('@theecryptochad/merge-guard');
const payload = JSON.parse('{"__proto__":{"isAdmin":true}}');
deepMerge({}, payload);
console.log({}.isAdmin); // true — Object.prototype is polluted
Impact
Any application using deepMerge() with untrusted input (e.g. user-supplied JSON from HTTP requests, WebSocket messages, or config files) is vulnerable. An attacker can inject arbitrary properties onto Object.prototype, enabling privilege escalation, application logic bypass, and property injection.
Remediation
Upgrade to @theecryptochad/merge-guard >= 1.0.1, which adds an explicit blocklist:
const BLOCKED = new Set(['__proto__', 'constructor', 'prototype']);
if (BLOCKED.has(key)) continue;
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @theecryptochad/merge-guard | all versions | 1.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @theecryptochad/merge-guard. 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 @theecryptochad/merge-guard to 1.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mhwj-73qx-jqxm 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-mhwj-73qx-jqxm 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-mhwj-73qx-jqxm. 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-mhwj-73qx-jqxm in your dependencies?
O3 detects GHSA-mhwj-73qx-jqxm across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.