{
  "cveId": "CVE-2026-82417",
  "url": "https://patchblox.com/security/cve/CVE-2026-82417",
  "summary": "CVE-2026-82417 is fixed in node-qs on 1 platform by DEBIAN-CVE-2026-82417 (version 6.16.0\u002Bds\u002B~6.15.1-1), released September 4, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "qs.stringify throws TypeError on objects with a non-callable constructor.isBuffer property",
  "description": "### Summary    \u0060qs.stringify\u0060 throws a \u0060TypeError\u0060 when it serializes an object whose own \u0060constructor\u0060 property has a truthy, non-callable \u0060isBuffer\u0060 member. \u0060utils.isBuffer\u0060 duck-types buffers by calling \u0060obj.constructor.isBuffer(obj)\u0060 after checking only that the property is truthy, so a value such as \u0060{ constructor: { isBuffer: \u0022x\u0022 } }\u0060 makes the call throw \u0060TypeError: obj.constructor.isBuffer is not a function\u0060.    ### Details    \u0060lib/stringify.js:127\u0060 calls \u0060utils.isBuffer\u0060 on every non-primitive value it serializes. \u0060utils.isBuffer\u0060 (\u0060lib/utils.js:332\u0060) reads \u0060obj.constructor.isBuffer\u0060 and invokes it without verifying that it is a function. \u0060constructor\u0060 and \u0060isBuffer\u0060 are ordinary property names, so any object carrying them as own properties reaches the unchecked call.    Such an object can be built from untrusted input. \u0060qs.parse(\u0022x[constructor][isBuffer]=y\u0022, { plainObjects: true })\u0060 or \u0060{ allowPrototypes: true }\u0060 keeps the \u0060constructor\u0060 key as an own property (the default parse options drop it), and \u0060JSON.parse(\u0022{\\\u0022a\\\u0022:{\\\u0022constructor\\\u0022:{\\\u0022isBuffer\\\u0022:\\\u0022x\\\u0022}}}\u0022)\u0060 produces the same shape with no qs option involved. Express 4 with its default \u0060query parser\u0060 setting and body-parser with \u0060extended: true\u0060 both call \u0060qs.parse\u0060 with \u0060allowPrototypes: true\u0060, so on those stacks \u0060req.query\u0060 and \u0060req.body\u0060 can carry the shape directly.    #### PoC    \u0060\u0060\u0060js    var qs = require(\u0022qs\u0022);    qs.stringify(qs.parse(\u0022x[constructor][isBuffer]=y\u0022, { plainObjects: true }));    qs.stringify(JSON.parse(\u0022{\\\u0022a\\\u0022:{\\\u0022constructor\\\u0022:{\\\u0022isBuffer\\\u0022:\\\u0022x\\\u0022}}}\u0022));    // TypeError: obj.constructor.isBuffer is not a function    //     at Object.isBuffer (lib/utils.js:332:78)    //     at stringify (lib/stringify.js:127:45)    \u0060\u0060\u0060    #### Fix    \u0060lib/utils.js\u0060, applied in e83d321 on \u0060main\u0060 and released as v6.16.0:    \u0060\u0060\u0060diff    - return !!(obj.constructor \u0026\u0026 obj.constructor.isBuffer \u0026\u0026 obj.constructor.isBuffer(obj));    \u002B return !!(obj.constructor \u0026\u0026 typeof obj.constructor.isBuffer === \u0022function\u0022 \u0026\u0026 obj.constructor.isBuffer(obj));    \u0060\u0060\u0060    Real \u0060Buffer\u0060, \u0060safer-buffer\u0060, and browserify \u0060buffer\u0060 polyfill instances serialize exactly as before; only the throw is removed.    ### Affected versions    \u0060\u003E=2.2.5 \u003C6.16.0\u0060, fixed in v6.16.0.    The unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used \u0060Buffer.isBuffer\u0060 and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call.    ### Impact    An unauthenticated request can make any code path that re-serializes attacker-influenced data with \u0060qs.stringify\u0060 (for example, rebuilding a query string from \u0060req.query\u0060 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 \u0060async\u0060 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.",
  "published": "2026-08-30T00:16:34Z",
  "severity": "Moderate",
  "cvss": 5.3,
  "cwe": "Uncaught Exception",
  "epss": 0.00396,
  "epssPercentile": 0.34065,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-82417",
  "fixes": [
    {
      "platform": "linux",
      "product": "node-qs",
      "release": "Debian 14",
      "fixedVersion": "6.16.0\u002Bds\u002B~6.15.1-1",
      "fix": "DEBIAN-CVE-2026-82417",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-82417",
      "released": "2026-09-04T01:46:23Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T19:38:12Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}