CVE-2025-15284 arrayLimit bypass in bracket notation allows DoS via memory exhaustion

What is CVE-2025-15284?

CVE-2025-15284 is a medium-severity denial of service vulnerability in qs_project:qs, published on 29 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-20

Which versions are affected by CVE-2025-15284?

2 open source packages ship an affected version, including qs. It affects 1 product.

Products include Qs Project Qs.

How do I fix CVE-2025-15284?

Upgrade qs to 6.14.1 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-15284 being exploited?

There is no known exploitation of CVE-2025-15284 in the wild and no public exploit code.

Other vulnerabilities in qs_project:qs

• CVE-2014-10064 Denial-of-Service Extended Event Loop Blocking in qs High 7.5
• CVE-2017-1000048 Prototype Pollution Protection Bypass in qs High 7.5
• CVE-2026-2391 qs's arrayLimit bypass in comma parsing allows denial of service Medium 6.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-73316, AZL-73319, AZL-73353, AZL-73359, CLEANSTART-2026-BM16290, CLSA-2026-1773274548 and 28 more.