qs array-limit bypass via bracket-key comma parsing

Exploitation

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

CVSS 4.0

6.3 · 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 · score source

EPSS

• CVE-2026-82562: 0.54% estimated exploitation activity in the next 30 days; percentile 45.49 (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 qs v6.15.3 allows bracket-key input to bypass arrayLimit and throwOnLimitExceeded when comma: true. The input a[]=1,2,3,4 succeeds with arrayLimit: 3, while the equivalent plain-key input is rejected. Affected version tested: Details parseArrayValue() enforces the comma limit only for flat values. The a[] form is marked non-flat, so its comma-separated value is wrapped after parsing and the inner array is not checked. A single parameter can therefore materialize arbitrarily large arrays. PoC On v6.15.3, the first input parses successfully and the second creates an array with 1,000,001 elements. The equivalent a=1,2,3,4 input throws RangeError as expected. Impact An attacker who can supply a query string or form body can bypass configured array limits and force excessive memory allocation, causing denial of service. The limit must be applied after comma splitting and before the resulting array is wrapped.

Published by the source

2 Sep 2026, 14:46 UTC

Last modified by the source

2 Sep 2026, 14:46 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-x5fp-wj9c-mxmx

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# Patch Next advisory brief: CVE-2026-82562

Advisory: qs array-limit bypass via bracket-key comma parsing
IDs: CVE-2026-82562, GHSA-x5fp-wj9c-mxmx
Record: https://patchnext.com/advisories/cve-2026-82562 (revision 1, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: qs 6.16.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm qs: affected >= 6.14.2, <= 6.15.3; fixed in 6.16.0

## 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://github.com/advisories/GHSA-x5fp-wj9c-mxmx (GitHub-reviewed advisory GHSA-x5fp-wj9c-mxmx lists affected ranges: npm qs >=6.14.2 <=6.15.3)

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