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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-2391: 0.54% estimated exploitation activity in the next 30 days; percentile 45.62 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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): The split(',') returns the array immediately, skipping the subsequent limit check. Downstream merging via utils.combine does not prevent allocation,…

Published by the source

12 Feb 2026, 17:04 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w7fw-mjwx-w883

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w7fw-mjwx-w883

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# Patch Next advisory brief: CVE-2026-2391

Advisory: qs's arrayLimit bypass in comma parsing allows denial of service
IDs: CVE-2026-2391, GHSA-w7fw-mjwx-w883
Record: https://patchnext.com/advisories/cve-2026-2391 (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: qs 6.14.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm qs: affected >= 6.7.0, <= 6.14.1; fixed in 6.14.2

## Suggested inspection (read-only)
- `npm ls qs --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on qs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w7fw-mjwx-w883 (OSV record GHSA-w7fw-mjwx-w883 lists affected ranges: npm qs >=6.7.0 <6.14.2 (fixed))
- Verified: https://github.com/advisories/GHSA-w7fw-mjwx-w883 (GitHub-reviewed advisory GHSA-w7fw-mjwx-w883 lists affected ranges: npm qs >=6.7.0 <=6.14.1)

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