deepHas vulnerable to Prototype Pollution via constructor.prototype
Date: 2026-01
Affected: npm/deephas
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2026-25047
CWE: CWE-1321

### Summary A prototype pollution vulnerability exists in version 1.0.7 of the deephas npm package that allows an attacker to modify global object behavior. This issue was fixed in version 1.0.8. ### Details The vulnerability resides in the `add()` function and `indexer()` function implemented within `deepHas.js`. Although version 1.0.7 attempts to prevent prototype pollution by checking property ownership (e.g., using Object.hasOwnProperty) and by checking against forbidden string usage (using String.prototype.indexOf), this check can be bypassed as shown in the PoC By doing so, an attacker can inject properties into Object.prototype through a payload such as constructor.prototype.polluted or __proto__.polluted resulting in prototype pollution. This issue affects all JavaScript runtimes that rely on npm packages (including Node.js, Deno, and Bun) and is independent of the operating system. ### PoC #### Steps to reproduce 1. Install version 1.0.7 of `deephas` using npm install 2. Run one of the following code snippets: ```javascript //PoC 1 Object.prototype.hasOwnProperty = () => true; console.log({}.polluted); const dh = require('deephas'); let obj = {}; dh.set(obj, 'constructor.prototype.polluted', 'yes'); console.log('{ ' + obj.polluted + ', ' + 'yes' + ' }'); // prints yes => the patch is bypassed and prototype pollution occurred ``` OR ```javascript //PoC 2 String.prototype.indexOf = () => -1; console.log({}.polluted); const dh = require('deephas'); let obj = {}; d


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