CVE-2026-8723 (Medium) detected in qs-6.14.2.tgz, qs-6.15.0.tgz

[mend-bolt-for-github]

CVE-2026-8723 - Medium Severity Vulnerability

Vulnerable Libraries - qs-6.14.2.tgz, qs-6.15.0.tgz

qs-6.14.2.tgz

A querystring parser that supports nesting and arrays, with a depth limit

Library home page: https://registry.npmjs.org/qs/-/qs-6.14.2.tgz

Path to dependency file: /OPENAPI-REST-API/swagger-client/nodejs-server/package.json

Path to vulnerable library: /OPENAPI-REST-API/swagger-client/nodejs-server/node_modules/express/node_modules/qs/package.json

Dependency Hierarchy:

• oas3-tools-2.2.3.tgz (Root Library)
  • express-4.22.1.tgz
    • ❌ qs-6.14.2.tgz (Vulnerable Library)

qs-6.15.0.tgz

A querystring parser that supports nesting and arrays, with a depth limit

Library home page: https://registry.npmjs.org/qs/-/qs-6.15.0.tgz

Path to dependency file: /OPENAPI-REST-API/openapi-client/javascript/package.json

Path to vulnerable library: /OPENAPI-REST-API/openapi-client/javascript/node_modules/qs/package.json,/OPENAPI-REST-API/swagger-client/javascript/node_modules/qs/package.json,/OPENAPI-REST-API/swagger-client/nodejs-server/node_modules/qs/package.json

Dependency Hierarchy:

• oas3-tools-2.2.3.tgz (Root Library)
  • ❌ qs-6.15.0.tgz (Vulnerable Library)

Found in HEAD commit: 1f70e2feccb7006c8d32cc7d4fe62f5cf5e5c34d

Found in base branch: master

Vulnerability 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" and released as v6.15.2:

• 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 <6.15.2" — fixed in v6.15.2.
  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").

Publish Date: 2026-05-16

URL: CVE-2026-8723

CVSS 3 Score Details (5.3)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-q8mj-m7cp-5q26

Release Date: 2026-05-16

Fix Resolution: qs - 6.15.2,qs - 6.15.2,https://github.com/ljharb/qs.git - v6.15.2

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