---
id: CVE-2025-15284
title: "Improper Input Validation vulnerability in qs (parse modules) allows HTTP DoS.This issue affects qs: < 6.14.1.\n\n\nSummary\n\nThe arrayLimit\_option in qs did not enforce limits for bracket notation (a[]=1&a[]=2), only for indexed notation (a…"
summary: "Improper Input Validation vulnerability in qs (parse modules) allows HTTP DoS.This issue affects qs: < 6.14.1.\n\n\nSummary\n\nThe arrayLimit\_option in qs did not enforce limits for bracket notation (a[]=1&a[]=2), only for indexed notation (a…"
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-20
vendor: qs_project
product: qs
affected:
  - qs < 6.14.1
patched:
  - qs 6.14.1
published: '2025-12-29'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T19:10:00.297'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-15284'
references:
  - url: >-
      https://github.com/ljharb/qs/commit/3086902ecf7f088d0d1803887643ac6c03d415b9
    label: 7ffcee3d-2c14-4c3e-b844-86c6a321a158
  - url: 'https://github.com/ljharb/qs/security/advisories/GHSA-6rw7-vpxm-498p'
    label: 7ffcee3d-2c14-4c3e-b844-86c6a321a158
tags:
  - nvd
epss: 0.0045
epssPercentile: 0.37491
ingestedAt: '2026-10-14T19:49:57.537Z'
---

## Overview

Improper Input Validation vulnerability in qs (parse modules) allows HTTP DoS.This issue affects qs: < 6.14.1.


Summary

The arrayLimit option in qs did not enforce limits for bracket notation (a[]=1&a[]=2), only for indexed notation (a[0]=1). This is a consistency bug; arrayLimit should apply uniformly across all array notations.

Note: The default parameterLimit of 1000 effectively mitigates the DoS scenario originally described. With default options, bracket notation cannot produce arrays larger than parameterLimit regardless of arrayLimit, because each a[]=valueconsumes one parameter slot. The severity has been reduced accordingly.

Details

The arrayLimit option only checked limits for indexed notation (a[0]=1&a[1]=2) but did not enforce it for bracket notation (a[]=1&a[]=2).

Vulnerable code (lib/parse.js:159-162):

if (root === '[]' && options.parseArrays) {
    obj = utils.combine([], leaf);  // No arrayLimit check
}





Working code (lib/parse.js:175):

else if (index <= options.arrayLimit) {  // Limit checked here
    obj = [];
    obj[index] = leaf;
}





The bracket notation handler at line 159 uses utils.combine([], leaf) without validating against options.arrayLimit, while indexed notation at line 175 checks index <= options.arrayLimit before creating arrays.



PoC

const qs = require('qs');
const result = qs.parse('a[]=1&a[]=2&a[]=3&a[]=4&a[]=5&a[]=6', { arrayLimit: 5 });
console.log(result.a.length);  // Output: 6 (should be max 5)





Note on parameterLimit interaction: The original advisory's "DoS demonstration" claimed a length of 10,000, but parameterLimit (default: 1000) caps parsing to 1,000 parameters. With default options, the actual output is 1,000, not 10,000.

Impact

Consistency bug in arrayLimit enforcement. With default parameterLimit, the practical DoS risk is negligible since parameterLimit already caps the total number of parsed parameters (and thus array elements from bracket notation). The risk increases only when parameterLimit is explicitly set to a very high value.

## Affected

- `qs < 6.14.1`

## Remediation

Upgrade past the affected range:

- `qs 6.14.1`