chore(deps): update dependency qs to v6.16.0 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
qs	6.14.0 → 6.16.0

---

qs's arrayLimit bypass in its bracket notation allows DoS via memory exhaustion

CVE-2025-15284 / GHSA-6rw7-vpxm-498p

More information

Details

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[]=value consumes 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.

Severity

• CVSS Score: 6.3 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L

References

• https://github.com/ljharb/qs/security/advisories/GHSA-6rw7-vpxm-498p
• https://nvd.nist.gov/vuln/detail/CVE-2025-15284
• https://github.com/ljharb/qs/commit/3086902ecf7f088d0d1803887643ac6c03d415b9
• https://github.com/advisories/GHSA-6rw7-vpxm-498p

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

qs's arrayLimit bypass in comma parsing allows denial of service

CVE-2026-2391 / GHSA-w7fw-mjwx-w883

More information

Details

Summary

The arrayLimit option in qs does not enforce limits for comma-separated values when comma: true is enabled, allowing attackers to cause denial-of-service via memory exhaustion. This is a bypass of the array limit enforcement, similar to the bracket notation bypass addressed in GHSA-6rw7-vpxm-498p (CVE-2025-15284).

Details

When the comma option is set to true (not the default, but configurable in applications), qs allows parsing comma-separated strings as arrays (e.g., ?param=a,b,c becomes ['a', 'b', 'c']). However, the limit check for arrayLimit (default: 20) and the optional throwOnLimitExceeded occur after the comma-handling logic in parseArrayValue, enabling a bypass. This permits creation of arbitrarily large arrays from a single parameter, leading to excessive memory allocation.

Vulnerable code (lib/parse.js: lines ~40-50):

if (val && typeof val === 'string' && options.comma && val.indexOf(',') > -1) {
    return val.split(',');
}

if (options.throwOnLimitExceeded && currentArrayLength >= options.arrayLimit) {
    throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');
}

return val;

The split(',') returns the array immediately, skipping the subsequent limit check. Downstream merging via utils.combine does not prevent allocation, even if it marks overflows for sparse arrays.This discrepancy allows attackers to send a single parameter with millions of commas (e.g., ?param=,,,,,,,,...), allocating massive arrays in memory without triggering limits. It bypasses the intent of arrayLimit, which is enforced correctly for indexed (a[0]=) and bracket (a[]=) notations (the latter fixed in v6.14.1 per GHSA-6rw7-vpxm-498p).

PoC

Test 1 - Basic bypass:

npm install qs

const qs = require('qs');

const payload = 'a=' + ','.repeat(25);  // 26 elements after split (bypasses arrayLimit: 5)
const options = { comma: true, arrayLimit: 5, throwOnLimitExceeded: true };

try {
  const result = qs.parse(payload, options);
  console.log(result.a.length);  // Outputs: 26 (bypass successful)
} catch (e) {
  console.log('Limit enforced:', e.message);  // Not thrown
}

Configuration:

• comma: true
• arrayLimit: 5
• throwOnLimitExceeded: true

Expected: Throws "Array limit exceeded" error.
Actual: Parses successfully, creating an array of length 26.

Impact

Denial of Service (DoS) via memory exhaustion.

Suggested Fix

Move the arrayLimit check before the comma split in parseArrayValue, and enforce it on the resulting array length. Use currentArrayLength (already calculated upstream) for consistency with bracket notation fixes.

Current code (lib/parse.js: lines ~40-50):

if (val && typeof val === 'string' && options.comma && val.indexOf(',') > -1) {
    return val.split(',');
}

if (options.throwOnLimitExceeded && currentArrayLength >= options.arrayLimit) {
    throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');
}

return val;

Fixed code:

if (val && typeof val === 'string' && options.comma && val.indexOf(',') > -1) {
    const splitArray = val.split(',');
    if (splitArray.length > options.arrayLimit - currentArrayLength) {  // Check against remaining limit
        if (options.throwOnLimitExceeded) {
            throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');
        } else {
            // Optionally convert to object or truncate, per README
            return splitArray.slice(0, options.arrayLimit - currentArrayLength);
        }
    }
    return splitArray;
}

if (options.throwOnLimitExceeded && currentArrayLength >= options.arrayLimit) {
    throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');
}

return val;

This aligns behavior with indexed and bracket notations, reuses currentArrayLength, and respects throwOnLimitExceeded. Update README to note the consistent enforcement.

Severity

• CVSS Score: 3.7 / 10 (Low)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

References

• https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883
• https://nvd.nist.gov/vuln/detail/CVE-2026-2391
• https://github.com/ljharb/qs/commit/f6a7abff1f13d644db9b05fe4f2c98ada6bf8482
• https://github.com/advisories/GHSA-w7fw-mjwx-w883

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

qs has a remotely triggerable DoS: qs.stringify crashes with TypeError on null/undefined entries in comma-format arrays when encodeValuesOnly is set

CVE-2026-8723 / GHSA-q8mj-m7cp-5q26

More information

Details

Summary

qs.stringify throws TypeError when called with arrayFormat: 'comma' and encodeValuesOnly: true on an array containing null or undefined. The throw is synchronous and not handled by any of qs's null-related options (skipNulls, strictNullHandling).

Details

In the comma + encodeValuesOnly branch, lib/stringify.js:145 mapped the array through the raw encoder before joining:

obj = utils.maybeMap(obj, encoder);

utils.encode (lib/utils.js:195) reads str.length with no null guard, so a null or undefined element throws TypeError. skipNulls and strictNullHandling are both checked in the per-element loop below this line and never get a chance to run.

Same class of bug as the filter-array path fixed in 0c180a4. The vulnerable shape of the comma + encodeValuesOnly branch was introduced in 4c4b23d ("encode comma values more consistently", PR #​463, 2023-01-19), first released in v6.11.1.

PoC

const qs = require('qs');

qs.stringify({ a: [null, 'b'] },      { arrayFormat: 'comma', encodeValuesOnly: true });
qs.stringify({ a: [undefined, 'b'] }, { arrayFormat: 'comma', encodeValuesOnly: true });
qs.stringify({ a: [null] },           { arrayFormat: 'comma', encodeValuesOnly: true });
// TypeError: Cannot read properties of null (reading 'length')
//     at encode (lib/utils.js:195:13)
//     at Object.maybeMap (lib/utils.js:322:37)
//     at stringify (lib/stringify.js:145:25)

Fix

lib/stringify.js:145, applied in 21f80b3 on main:

- obj = utils.maybeMap(obj, encoder);
+ obj = utils.maybeMap(obj, function (v) {
+     return v == null ? v : encoder(v);
+ });

null and undefined now pass through maybeMap unchanged and reach the join(',') step as-is. For { a: [null, 'b'] } this produces a=,b, matching the non-encodeValuesOnly comma path (which already joins before encoding and produces a=%2Cb for the same input). Single-element [null] arrays still collapse via the existing obj.join(',') || null and remain subject to skipNulls / strictNullHandling in the main loop.

Affected versions

>=6.11.1 <=6.15.1

The vulnerable code shape was introduced in 4c4b23d and first shipped in v6.11.1. Earlier versions — including all of 6.7.x, 6.8.x, 6.9.x, 6.10.x, and 6.11.0 — implemented the comma + encodeValuesOnly path differently (joining before encoding) and are not affected. Empirically verified across released versions.

Impact

Application code that calls qs.stringify with both arrayFormat: 'comma' and encodeValuesOnly: true (both non-default) on input that may contain a null or undefined array element will throw synchronously instead of producing a query string. In a typical Node.js HTTP framework (Express, Fastify, Koa, hapi) the sync throw is caught by the framework's error boundary and the affected request returns a 500; the worker process does not exit and subsequent requests are unaffected. The "kills the worker process" framing applies only to call sites outside a request-handler error boundary (background jobs, startup paths, stream pipelines) or to deployments with framework error handling explicitly disabled.

The vulnerable input is a null or undefined entry inside an array; this is reachable from JSON request bodies or from application code constructing arrays from user input, but not from standard HTML form submissions (which produce strings or omitted fields, not literal null).

Severity

• CVSS Score: 6.3 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

• https://github.com/ljharb/qs/security/advisories/GHSA-q8mj-m7cp-5q26
• https://nvd.nist.gov/vuln/detail/CVE-2026-8723
• https://github.com/ljharb/qs/commit/21f80b33e5c8b3f7eba1034fff0da4a4a37a1d41
• https://github.com/advisories/GHSA-q8mj-m7cp-5q26

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

qs: Denial of Service via Attacker Controlled isBuffer

CVE-2026-82417 / GHSA-4mjr-xmp4-gh2g

More information

Details

Summary

qs.stringify() calls utils.isBuffer() on every value it serializes, and utils.isBuffer() invokes obj.constructor.isBuffer(obj) without checking that it is callable. A value whose own constructor.isBuffer is a non-function makes qs call a non-callable and throw TypeError. Such a value is produced by qs.parse itself from an untrusted query string when plainObjects: true or allowPrototypes: true is set, so a pure-qs parse → stringify round-trip — no JSON.parse — turns an unauthenticated query string into an uncaught throw.

An attacker-controlled parse input reaches the host application's availability asset — via qs's own recommended plainObjects mitigation — and triggers an uncaught exception during a parse → stringify round-trip.

Details

utils.isBuffer runs at lib/stringify.js:127 for every serialized value:

if (isNonNullishPrimitive(obj) || utils.isBuffer(obj)) { ... }

utils.isBuffer (lib/utils.js:327-333) invokes obj.constructor.isBuffer without verifying it is callable:

var isBuffer = function isBuffer(obj) {
    if (!obj || typeof obj !== 'object') { return false; }
    return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));
};

constructor and isBuffer are ordinary keys. qs.parse with plainObjects: true or allowPrototypes: true keeps them as own properties, so the parsed value carries a non-function constructor.isBuffer; stringify then calls a non-callable and throws TypeError. By contrast utils.isRegExp uses a brand check (Object.prototype.toString); the missing guard here is an internal inconsistency, not a platform limitation.

Trust Boundary Note

qs.stringify alone treats its input as caller-constructed, so serializing a hostile object could be argued outside its contract. This report does not depend on that framing: the malicious shape is produced by qs.parse, whose input is untrusted by design. qs.parse normally strips a constructor key via its prototype guard, but with the documented options plainObjects: true or allowPrototypes: true the key survives and lands as an own property. Feeding the parsed object back into qs.stringify — the standard round-trip in gateways and request-forwarders — then hits the unchecked call.

PoC

poc02c_isBuffer_qs_only_roundtrip.js — pure-qs chain, no JSON.parse; an untrusted query string alone reaches the throw:

'use strict';
var qs = require('qs');

var untrustedQueryString = 'x%5Bconstructor%5D%5BisBuffer%5D=y'; // x[constructor][isBuffer]=y

var parsed = qs.parse(untrustedQueryString, { plainObjects: true });
console.log('[parse] kept constructor key:', JSON.stringify(parsed));

try {
    qs.stringify(parsed);
    console.log('[stringify] no throw (unexpected)');
} catch (e) {
    console.log('[stringify] DoS reproduced ->', e.constructor.name + ':', e.message);
}

poc02_isBuffer.js — the minimal defect:

'use strict';
var qs = require('qs');
try {
    qs.stringify(JSON.parse('{"a":{"constructor":{"isBuffer":"x"}}}'));
} catch (e) {
    console.log('[A] DoS reproduced ->', e.constructor.name + ':', e.message);
}

poc02b_isBuffer_async_crash.js — worker death in an async sink:

'use strict';
var qs = require('qs');

function handleRequestAsync(clientJsonBody) {
    try {
        setImmediate(function () {                 // async continuation, outside the try
            qs.stringify(JSON.parse(clientJsonBody)); // throws here, uncaught
        });
        console.log('[handler] returned 200 synchronously; async work scheduled');
    } catch (e) {
        console.log('[handler] caught synchronously (will NOT happen):', e.message);
    }
}
process.on('exit', function (code) {
    console.log('[proc] process exiting with code:', code);
});
handleRequestAsync('{"filters":{"constructor":{"isBuffer":"x"}}}');

Execution Steps

cd poc
npm install qs@6.15.3
node poc02c_isBuffer_qs_only_roundtrip.js  # pure qs parse->stringify -> TypeError
node poc02_isBuffer.js                      # minimal defect -> TypeError inside stringify
node poc02b_isBuffer_async_crash.js         # async sink -> uncaught throw -> exit code 1

Reproduction Evidence

poc02c_isBuffer_qs_only_roundtrip.js :

[parse] kept constructor key: {"x":{"constructor":{"isBuffer":"y"}}}
[stringify] DoS reproduced -> TypeError: obj.constructor.isBuffer is not a function

poc02_isBuffer.js:

[A] DoS reproduced -> TypeError: obj.constructor.isBuffer is not a function

poc02b_isBuffer_async_crash.js :

[handler] returned 200 synchronously; async work scheduled
[proc] process exiting with code: 1
TypeError: obj.constructor.isBuffer is not a function
    at Object.isBuffer (.../qs/lib/utils.js:332:78)
    at stringify (.../qs/lib/stringify.js:127:45)
=== EXIT CODE: 1 ===

The pure-qs round-trip shows the malicious shape originates from qs.parse of an untrusted query string, with no JSON.parse. The synchronous try/catch in the async case does not catch the throw; the process exits with code 1, denying service to all requests on that worker.

Impact

An unauthenticated request degrades any endpoint that re-serializes deserialized client data with qs.stringify. The primary impact is a per-request failure: the handler throws and the framework returns HTTP 500. Where the call sits in an unguarded async continuation, the throw escapes and the worker process exits, denying service to all requests it was handling, which means a higher impact that depends on the application's error handling, not on qs.

Recommended Fix

Replace the duck-type with a brand check mirroring utils.isRegExp:

var isBuffer = function isBuffer(obj) {
    if (!obj || typeof obj !== 'object') { return false; }
    if (typeof Buffer !== 'undefined' && typeof Buffer.isBuffer === 'function') {
        return Buffer.isBuffer(obj);
    }
    return Object.prototype.toString.call(obj) === '[object Uint8Array]';
};

If duck-typing must remain, require typeof obj.constructor.isBuffer === 'function' before invoking and wrap the call in try/catch.

Severity

• CVSS Score: 6.3 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

• https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g
• https://nvd.nist.gov/vuln/detail/CVE-2026-82417
• https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6
• https://github.com/advisories/GHSA-4mjr-xmp4-gh2g

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Release Notes

ljharb/qs (qs)

v6.16.0

Compare Source

• [New] stringify: add a depth option to bound recursion depth (default Infinity)
• [Fix] stringify: serialize Date values when a filter is provided
• [Fix] parse: enforce arrayLimit on comma groups under []= when throwOnLimitExceeded is set
• [Fix] parse: flatten a collection appended to an overflowed array (#​571)
• [Fix] utils: isBuffer: do not invoke a non-callable constructor.isBuffer
• [Fix] stringify: do not let allowEmptyArrays skip cycle detection (or drop own keys) on an empty array with own properties
• [Fix] stringify: encode dots in a top-level key with a primitive value when encodeDotInKeys is set (#​562)
• [Docs] threat model: clarify stringify deep-nesting DoS is caller-bounded
• [Docs] clarify arrayLimit is a representation threshold, not an element-count cap
• [Tests] parse: remove a test that pinned []= comma groups escaping arrayLimit
• [Tests] stringify: pin current encodeDotInKeys separator-dot behavior
• [Dev Deps] update @ljharb/eslint-config, eslint
• [Dev Deps] update eslint, evalmd

v6.15.3

Compare Source

• [Fix] parse: enforce throwOnLimitExceeded for cumulative array growth via combine/merge
• [Fix] utils: respect encoding of surrogate pairs across chunks (#​559)
• [Robustness] parse: throw the arrayLimit error before splitting oversized comma values
• [Robustness] utils.merge / utils.assign: avoid invoking __proto__ setter when copying own properties
• [Robustness] utils: enforce arrayLimit consistently across merge's array paths
• [Perf] utils: make compact O(n) via a side-channel visited-set instead of Array.indexOf
• [Deps] update side-channel
• [Dev Deps] update eslint, mock-property, tape
• [Tests] parse: characterize current lenient handling of unbalanced bracket keys (#​558)

v6.15.2

Compare Source

• [Fix] stringify: skip null/undefined entries in arrayFormat: 'comma' + encodeValuesOnly instead of crashing in encoder
• [Fix] stringify: use configured delimiter after charsetSentinel (#​555)
• [Fix] stringify: apply formatter to encoded key under strictNullHandling (#​554)
• [Fix] stringify: skip null/undefined filter-array entries instead of crashing in encoder (#​551)
• [Fix] parse: handle nested bracket groups and add regression tests (#​530)
• [readme] fix grammar (#​550)
• [Dev Deps] update @ljharb/eslint-config
• [Tests] add regression tests for keys containing percent-encoded bracket text

v6.15.1

Compare Source

• [Fix] parse: parameterLimit: Infinity with throwOnLimitExceeded: true silently drops all parameters
• [Deps] update @ljharb/eslint-config
• [Dev Deps] update @ljharb/eslint-config, iconv-lite
• [Tests] increase coverage

v6.15.0

Compare Source

• [New] parse: add strictMerge option to wrap object/primitive conflicts in an array (#​425, #​122)
• [Fix] duplicates option should not apply to bracket notation keys (#​514)

v6.14.2

Compare Source

• [Fix] parse: mark overflow objects for indexed notation exceeding arrayLimit (#​546)
• [Fix] arrayLimit means max count, not max index, in combine/merge/parseArrayValue
• [Fix] parse: throw on arrayLimit exceeded with indexed notation when throwOnLimitExceeded is true (#​529)
• [Fix] parse: enforce arrayLimit on comma-parsed values
• [Fix] parse: fix error message to reflect arrayLimit as max index; remove extraneous comments (#​545)
• [Robustness] avoid .push, use void
• [readme] document that addQueryPrefix does not add ? to empty output (#​418)
• [readme] clarify parseArrays and arrayLimit documentation (#​543)
• [readme] replace runkit CI badge with shields.io check-runs badge
• [meta] fix changelog typo (arrayLength → arrayLimit)
• [actions] fix rebase workflow permissions

v6.14.1

Compare Source

• [Fix] ensure arrayLimit applies to [] notation as well
• [Fix] parse: when a custom decoder returns null for a key, ignore that key
• [Refactor] parse: extract key segment splitting helper
• [meta] add threat model
• [actions] add workflow permissions
• [Tests] stringify: increase coverage
• [Dev Deps] update eslint, @ljharb/eslint-config, npmignore, es-value-fixtures, for-each, object-inspect

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Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	qs@​6.14.0 ⏵ 6.15.2		+3

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The artifact failure details are included below:

File name: pnpm-lock.yaml

Error: ERR_PNPM_UPDATE_VERSION_ON_INDIRECT_DEP

  × updating dependencies
  ╰─▶ "qs" (requested "6.16.0") is not a direct dependency, so the requested
      version cannot be recorded.
  help: An update resolves a transitive dependency the way a fresh install
        would, so a version on the command line has no effect on it. To pin
        one, add an override scoped to the range its dependents declare to
        pnpm-workspace.yaml:
        
          overrides:
            qs@<declared range>: 6.16.0
        
        To update it within the range its dependents already declare, drop the
        version: pnpm update qs