Vulnerabilities in pkg:npm/@theecryptochad/merge-guard

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mhwj-73qx-jqxm",
  "modified" : "2026-05-11T16:10:12Z",
  "published" : "2026-05-11T16:10:12Z",
  "aliases" : [ ],
  "summary" : "@theecryptochad/merge-guard has Prototype Pollution in its deepMerge() function",
  "details" : "## Summary\n\n`@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.\n\n## Details\n\nThe `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`.\n\n## Proof of Concept\n\n```js\nconst { deepMerge } = require('@theecryptochad/merge-guard');\nconst payload = JSON.parse('{\"__proto__\":{\"isAdmin\":true}}');\ndeepMerge({}, payload);\nconsole.log({}.isAdmin); // true — Object.prototype is polluted\n```\n\n## Impact\n\nAny 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.\n\n## Remediation\n\nUpgrade to `@theecryptochad/merge-guard >= 1.0.1`, which adds an explicit blocklist:\n\n```js\nconst BLOCKED = new Set(['__proto__', 'constructor', 'prototype']);\nif (BLOCKED.has(key)) continue;\n```\n\n## References\n- [CWE-1321: Improper Neutralization of Special Elements in Object Keys](https://cwe.mitre.org/data/definitions/1321.html)\n- [OWASP: Prototype Pollution](https://owasp.org/www-community/attacks/Prototype_Pollution)\n- [Fix commit](https://github.com/TheeCryptoChad/merge-guard/releases/tag/v1.0.1)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@theecryptochad/merge-guard"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/TheeCryptoChad/merge-guard/security/advisories/GHSA-mhwj-73qx-jqxm"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/TheeCryptoChad/merge-guard/commit/25e4b4f2618578a656ef3cb4946a1b475f736736"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/TheeCryptoChad/merge-guard"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-11T16:10:12Z",
    "nvd_published_at" : null
  }
}