Update dependency qs to v6.15.2 [SECURITY] (release/1.6-alpha)

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
qs	6.14.0 → 6.15.2

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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/ljharb/qs

This data is provided by OSV and 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/ljharb/qs

This data is provided by OSV and 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/ljharb/qs

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

---

Release Notes

ljharb/qs (qs)

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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