{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2026-82417",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-82417",
    "idYear": 2026,
    "status": "PUBLISHED",
    "publishedAt": "2026-08-29T23:51:27.634Z",
    "updatedAt": "2026-08-31T17:08:24.074Z",
    "importedAt": "2026-10-24T01:58:30.346Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "qs.stringify throws TypeError on objects with a non-callable constructor.isBuffer property",
      "summary": "### Summary\n\n\n\n`qs.stringify` throws a `TypeError` when it serializes an object whose own `constructor` property has a truthy, non-callable `isBuffer` member. `utils.isBuffer` duck-types buffers by calling `obj.constructor.isBuffer(obj)` after checking only that the property is truthy, so a value such as `{ constructor: { isBuffer: \"x\" } }` makes the call throw `TypeError: obj.constructor.isBuffer is not a function`.\n\n\n\n### Details\n\n\n\n`lib/stringify.js:127` calls `utils.isBuffer` on every non-primitive value it serializes. `utils.isBuffer` (`lib/utils.js:332`) reads `obj.constructor.isBuffer` and invokes it without verifying that it is a function. `constructor` and `isBuffer` are ordinary property names, so any object carrying them as own properties reaches the unchecked call.\n\n\n\nSuch an object can be built from untrusted input. `qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true })` or `{ allowPrototypes: true }` keeps the `constructor` key as an own property (the default parse options drop it), and `JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\")` produces the same shape with no qs option involved. Express 4 with its default `query parser` setting and body-parser with `extended: true` both call `qs.parse` with `allowPrototypes: true`, so on those stacks `req.query` and `req.body` can carry the shape directly.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nqs.stringify(qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true }));\n\n\n\nqs.stringify(JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\"));\n\n\n\n// TypeError: obj.constructor.isBuffer is not a function\n\n\n\n//     at Object.isBuffer (lib/utils.js:332:78)\n\n\n\n//     at stringify (lib/stringify.js:127:45)\n\n\n\n```\n\n\n\n#### Fix\n\n\n\n`lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0:\n\n\n\n```diff\n\n\n\n- return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));\n\n\n\n+ return !!(obj.constructor && typeof obj.constructor.isBuffer === \"function\" && obj.constructor.isBuffer(obj));\n\n\n\n```\n\n\n\nReal `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed.\n\n\n\n### Affected versions\n\n\n\n`>=2.2.5 <6.16.0`, fixed in v6.16.0.\n\n\n\nThe unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used `Buffer.isBuffer` and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call.\n\n\n\n### Impact\n\n\n\nAn unauthenticated request can make any code path that re-serializes attacker-influenced data with `qs.stringify` (for example, rebuilding a query string from `req.query` for a redirect or an upstream request, or serializing a parsed JSON body) throw synchronously. In a typical Node.js HTTP framework the throw is caught by the framework error boundary and the affected request returns a 500; the process survives and other requests are unaffected. Where the call runs outside an error boundary, such as an `async` Express 4 handler (where the throw becomes an unhandled promise rejection) or a background job, the process exits, so the impact in that case depends on the application error handling rather than on qs.",
      "affected": [
        {
          "vendor": "ljharb",
          "product": "qs",
          "packageName": "qs",
          "collectionURL": "https://npmjs.com/qs",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "2.2.5",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "6.16.0"
            }
          ]
        }
      ]
    }
  }
}