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Fencer Vulns
low 3.7

CVE-2026-2391 json

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

published 2026-02-12 8 mo ago modified 2026-09-10 1 mo ago also GHSA-w7fw-mjwx-w883 , EUVD-2026-6720

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

### 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): ```js 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 ```

```js 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.

Patch / fix

  • npm qs 6.14.2
  • qs_project qs 6.14.2
  • node-qs Debian 14 6.15.0+ds+~6.15.0-1

debian advisories DEBIAN-CVE-2026-2391

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-2391 updated cvss 5.3

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

  • Red Hat Cryostat 4 io.cryostat-cryostat, cryostat/cryostat-openshift-console-plugin-rhel9 Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/vector-rhel9, openshift-logging/fluentd-rhel9, openshift-logging/kibana6-rhel8, openshift-logging/eventrouter-rhel9, openshift-logging/elasticsearch6-rhel9, openshift-logging/logging-curator5-rhel9, +7 more Red Hat Migration Toolkit for Applications 8 mta/mta-ui-rhel9 Red Hat Node HealthCheck Operator workload-availability/node-remediation-console-rhel8 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9 Red Hat OpenShift Pipelines openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-api-rhel8, openshift-pipelines/pipelines-hub-db-migration-rhel8
    +12 more products
    Red Hat 3scale API Management Platform 2 3scale-amp20/system, 3scale-amp21/system, 3scale-amp22/system, 3scale-amp24/system, 3scale-amp25/system, 3scale-amp26/system, +3 more Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/volsync-rhel9, rhacm2/volsync-operator-bundle Red Hat AMQ Broker 7 org.jolokia-jolokia-parent Red Hat Ansible Automation Platform 2 ansible-automation-platform-24/lightspeed-rhel8, ansible-automation-platform-25/lightspeed-rhel8, ansible-automation-platform/automation-dashboard-rhel9 Red Hat build of Apache Camel - HawtIO 4 io.hawt-project Red Hat build of Apicurio Registry 2 io.apicurio-apicurio-registry Red Hat build of OptaPlanner 8 org.optaweb.vehiclerouting-optaweb-vehicle-routing Red Hat Data Grid 8 org.infinispan-infinispan-console Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Discovery 2 discovery/discovery-ui-rhel9 Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 pcs, firefox, grafana, mozjs60, pcs-snmp, thunderbird, +13 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 9 gjs, pcs, polkit, firefox, grafana, sgx-mpa, +12 more
    affected: workaround, no fix available, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 10 gjs, firefox, linux-sgx, thunderbird Red Hat Fuse 7 io.hawt-project, io.apicurio-apicurito, io.hawt-hawtio-online, io.syndesis-syndesis-ui, io.hawt-hawtio-integration, io.syndesis-syndesis-parent Red Hat JBoss Enterprise Application Platform 7 io.hawt-project, org.jboss.hal-hal-parent Red Hat JBoss Enterprise Application Platform 8 io.hawt-project, org.keycloak-keycloak-parent, io.smallrye-smallrye-open-api-parent Red Hat JBoss Enterprise Application Platform Expansion Pack io.hawt-project, org.keycloak-keycloak-parent, io.smallrye-smallrye-open-api-parent Red Hat OpenShift AI (RHOAI) rhoai/odh-data-science-pipelines-argo-argoexec-rhel8, rhoai/odh-data-science-pipelines-argo-workflowcontroller-rhel8
    +7 more products
    Red Hat OpenShift Container Platform 4 openshift4/ose-console-rhel9 Red Hat Openshift Data Foundation 4 odf4/mcg-core-rhel9 Red Hat OpenShift Dev Spaces devspaces/dashboard-rhel9 Red Hat Process Automation 7 org.uberfire-uberfire-parent, org.kie.workbench-kie-wb-common, org.kie-process-migration-service Red Hat Quay 3 quay/quay-rhel8 Red Hat streams for Apache Kafka 2 com.github.streamshub-console Red Hat streams for Apache Kafka 3 com.github.streamshub-console
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 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
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
CNA 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
npm qs
>=6.7.0, <6.14.2
6.14.2

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.