qs : qs.stringify with arrayFormat 'comma' throws an uncaught TypeError on array elements carrying a non-callable own toString (DoS)

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-2026-110816: 0.37% estimated exploitation activity in the next 30 days; percentile 30.75 (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.stringify(obj, { arrayFormat: 'comma' }) throws an uncaught TypeError: Cannot convert object to primitive value when an array in obj contains an element that carries an own, non-callable toString property (for example { a: [ { toString: 'x' } ] }). A remote, unauthenticated attacker who can influence an object that the application later re-serializes with the comma array format triggers the throw. In a service that lacks a synchronous error boundary around the serialization call, the uncaught exception crashes the worker process, producing a denial of service. Root Cause When arrayFormat: 'comma' is selected, the comma branch collapses the whole array into a single value via Array.prototype.join, or, under encodeValuesOnly: true, maps each element through the value encoder before joining. Both paths perform an implicit string coercion (ToPrimitive with hint "string") on each element. For an object whose own toString is a non-callable value, coercion skips the shadowed…

Published by the source

27 Oct 2026, 16:10 UTC

Last modified by the source

29 Oct 2026, 02:22 UTC

Source last checked

29 Oct 2026, 03:10 UTC

1. Revision 3 · amended · 29 Oct 2026

   Amended from ghsa record GHSA-6pq8-jhm2-2vcw

2. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-6pq8-jhm2-2vcw

3. Revision 1 · created · 27 Oct 2026

   Published from ghsa record GHSA-6pq8-jhm2-2vcw

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# Patch Next advisory brief: CVE-2026-110816

Advisory: qs : qs.stringify with arrayFormat 'comma' throws an uncaught TypeError on array elements carrying a non-callable own toString (DoS)
IDs: CVE-2026-110816, GHSA-6pq8-jhm2-2vcw
Record: https://patchnext.com/advisories/cve-2026-110816 (revision 3, source checked 29 Oct 2026, 03:10 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 6.16.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm qs: affected >= 6.7.0, <= 6.16.0; fixed in 6.16.1

## 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-6pq8-jhm2-2vcw (GitHub-reviewed advisory GHSA-6pq8-jhm2-2vcw lists affected ranges: npm qs >=6.7.0 <=6.16.0)
- Verified: https://osv.dev/vulnerability/GHSA-6pq8-jhm2-2vcw (OSV record GHSA-6pq8-jhm2-2vcw lists affected ranges: npm qs >=6.7.0 <6.16.1 (fixed))

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