CVE-2026-8723 (GCVE-0-2026-8723)
Vulnerability from cvelistv5
Published
2026-05-16 23:21
Modified
2026-05-18 14:02
Severity ?
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
6.3 (Medium) - 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
CWE
  • CWE-476 - NULL Pointer Dereference
Summary
### 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: ```js 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 ```js 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: ```diff - 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`).
References
Impacted products
Vendor Product Version
ljharb qs Version: 6.11.1   ≤
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              "value": "\u003cp\u003e### Summary\u003c/p\u003e\u003cp\u003e`qs.stringify` throws `TypeError` when called with `arrayFormat: \u0027comma\u0027` and `encodeValuesOnly: true` on an array containing `null` or `undefined`. The throw is synchronous and not handled by any of qs\u0027s null-related options (`skipNulls`, `strictNullHandling`).\u003c/p\u003e\u003cp\u003e### Details\u003c/p\u003e\u003cp\u003eIn the comma + `encodeValuesOnly` branch, `lib/stringify.js:145` mapped the array through the raw encoder before joining:\u003c/p\u003e\u003cp\u003e```js\u003c/p\u003e\u003cp\u003eobj = utils.maybeMap(obj, encoder);\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e`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.\u003c/p\u003e\u003cp\u003eSame 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.\u003c/p\u003e\u003cp\u003e#### PoC\u003c/p\u003e\u003cp\u003e```js\u003c/p\u003e\u003cp\u003econst qs = require(\u0027qs\u0027);\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [null, \u0027b\u0027] },      { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [undefined, \u0027b\u0027] }, { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [null] },           { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003e// TypeError: Cannot read properties of null (reading \u0027length\u0027)\u003c/p\u003e\u003cp\u003e//     at encode (lib/utils.js:195:13)\u003c/p\u003e\u003cp\u003e//     at Object.maybeMap (lib/utils.js:322:37)\u003c/p\u003e\u003cp\u003e//     at stringify (lib/stringify.js:145:25)\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e#### Fix\u003c/p\u003e\u003cp\u003e`lib/stringify.js:145`, applied in 21f80b3 on `main` and released as v6.15.2:\u003c/p\u003e\u003cp\u003e```diff\u003c/p\u003e\u003cp\u003e- obj = utils.maybeMap(obj, encoder);\u003c/p\u003e\u003cp\u003e+ obj = utils.maybeMap(obj, function (v) {\u003c/p\u003e\u003cp\u003e+     return v == null ? v : encoder(v);\u003c/p\u003e\u003cp\u003e+ });\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e`null` and `undefined` now pass through `maybeMap` unchanged and reach the `join(\u0027,\u0027)` step as-is. For `{ a: [null, \u0027b\u0027] }` 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(\u0027,\u0027) || null` and remain subject to `skipNulls` / `strictNullHandling` in the main loop.\u003c/p\u003e\u003cp\u003e### Affected versions\u003c/p\u003e\u003cp\u003e`\u0026gt;=6.11.1 \u0026lt;6.15.2` \u2014 fixed in v6.15.2.\u003c/p\u003e\u003cp\u003eThe vulnerable code shape was introduced in 4c4b23d and first shipped in v6.11.1. Earlier versions \u2014 including all of 6.7.x, 6.8.x, 6.9.x, 6.10.x, and 6.11.0 \u2014 implemented the comma + `encodeValuesOnly` path differently (joining before encoding) and are not affected. Empirically verified across released versions.\u003c/p\u003e\u003cp\u003e### Impact\u003c/p\u003e\u003cp\u003eApplication code that calls `qs.stringify` with both `arrayFormat: \u0027comma\u0027` 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\u0027s 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.\u003c/p\u003e\u003cp\u003eThe 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`).\u003c/p\u003e"
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      "title": "qs.stringify crashes on null/undefined entries in comma-format arrays under encodeValuesOnly"
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The throw is synchronous and not handled by any of qs\u0027s null-related options (`skipNulls`, `strictNullHandling`).\\n\\n\\n\\n### Details\\n\\n\\n\\nIn the comma + `encodeValuesOnly` branch, `lib/stringify.js:145` mapped the array through the raw encoder before joining:\\n\\n\\n\\n```js\\n\\n\\n\\nobj = utils.maybeMap(obj, encoder);\\n\\n\\n\\n```\\n\\n\\n\\n`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.\\n\\n\\n\\nSame 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.\\n\\n\\n\\n#### PoC\\n\\n\\n\\n```js\\n\\n\\n\\nconst qs = require(\u0027qs\u0027);\\n\\n\\n\\nqs.stringify({ a: [null, \u0027b\u0027] },      { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\\n\\n\\n\\nqs.stringify({ a: [undefined, \u0027b\u0027] }, { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\\n\\n\\n\\nqs.stringify({ a: [null] },           { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\\n\\n\\n\\n// TypeError: Cannot read properties of null (reading \u0027length\u0027)\\n\\n\\n\\n//     at encode (lib/utils.js:195:13)\\n\\n\\n\\n//     at Object.maybeMap (lib/utils.js:322:37)\\n\\n\\n\\n//     at stringify (lib/stringify.js:145:25)\\n\\n\\n\\n```\\n\\n\\n\\n#### Fix\\n\\n\\n\\n`lib/stringify.js:145`, applied in 21f80b3 on `main` and released as v6.15.2:\\n\\n\\n\\n```diff\\n\\n\\n\\n- obj = utils.maybeMap(obj, encoder);\\n\\n\\n\\n+ obj = utils.maybeMap(obj, function (v) {\\n\\n\\n\\n+     return v == null ? v : encoder(v);\\n\\n\\n\\n+ });\\n\\n\\n\\n```\\n\\n\\n\\n`null` and `undefined` now pass through `maybeMap` unchanged and reach the `join(\u0027,\u0027)` step as-is. For `{ a: [null, \u0027b\u0027] }` 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(\u0027,\u0027) || null` and remain subject to `skipNulls` / `strictNullHandling` in the main loop.\\n\\n\\n\\n### Affected versions\\n\\n\\n\\n`\u003e=6.11.1 \u003c6.15.2` \\u2014 fixed in v6.15.2.\\n\\n\\n\\nThe vulnerable code shape was introduced in 4c4b23d and first shipped in v6.11.1. Earlier versions \\u2014 including all of 6.7.x, 6.8.x, 6.9.x, 6.10.x, and 6.11.0 \\u2014 implemented the comma + `encodeValuesOnly` path differently (joining before encoding) and are not affected. Empirically verified across released versions.\\n\\n\\n\\n### Impact\\n\\n\\n\\nApplication code that calls `qs.stringify` with both `arrayFormat: \u0027comma\u0027` 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\u0027s 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.\\n\\n\\n\\nThe 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`).\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003e### Summary\u003c/p\u003e\u003cp\u003e`qs.stringify` throws `TypeError` when called with `arrayFormat: \u0027comma\u0027` and `encodeValuesOnly: true` on an array containing `null` or `undefined`. The throw is synchronous and not handled by any of qs\u0027s null-related options (`skipNulls`, `strictNullHandling`).\u003c/p\u003e\u003cp\u003e### Details\u003c/p\u003e\u003cp\u003eIn the comma + `encodeValuesOnly` branch, `lib/stringify.js:145` mapped the array through the raw encoder before joining:\u003c/p\u003e\u003cp\u003e```js\u003c/p\u003e\u003cp\u003eobj = utils.maybeMap(obj, encoder);\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e`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.\u003c/p\u003e\u003cp\u003eSame 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.\u003c/p\u003e\u003cp\u003e#### PoC\u003c/p\u003e\u003cp\u003e```js\u003c/p\u003e\u003cp\u003econst qs = require(\u0027qs\u0027);\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [null, \u0027b\u0027] },      { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [undefined, \u0027b\u0027] }, { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003eqs.stringify({ a: [null] },           { arrayFormat: \u0027comma\u0027, encodeValuesOnly: true });\u003c/p\u003e\u003cp\u003e// TypeError: Cannot read properties of null (reading \u0027length\u0027)\u003c/p\u003e\u003cp\u003e//     at encode (lib/utils.js:195:13)\u003c/p\u003e\u003cp\u003e//     at Object.maybeMap (lib/utils.js:322:37)\u003c/p\u003e\u003cp\u003e//     at stringify (lib/stringify.js:145:25)\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e#### Fix\u003c/p\u003e\u003cp\u003e`lib/stringify.js:145`, applied in 21f80b3 on `main` and released as v6.15.2:\u003c/p\u003e\u003cp\u003e```diff\u003c/p\u003e\u003cp\u003e- obj = utils.maybeMap(obj, encoder);\u003c/p\u003e\u003cp\u003e+ obj = utils.maybeMap(obj, function (v) {\u003c/p\u003e\u003cp\u003e+     return v == null ? v : encoder(v);\u003c/p\u003e\u003cp\u003e+ });\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e`null` and `undefined` now pass through `maybeMap` unchanged and reach the `join(\u0027,\u0027)` step as-is. For `{ a: [null, \u0027b\u0027] }` 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(\u0027,\u0027) || null` and remain subject to `skipNulls` / `strictNullHandling` in the main loop.\u003c/p\u003e\u003cp\u003e### Affected versions\u003c/p\u003e\u003cp\u003e`\u0026gt;=6.11.1 \u0026lt;6.15.2` \\u2014 fixed in v6.15.2.\u003c/p\u003e\u003cp\u003eThe vulnerable code shape was introduced in 4c4b23d and first shipped in v6.11.1. Earlier versions \\u2014 including all of 6.7.x, 6.8.x, 6.9.x, 6.10.x, and 6.11.0 \\u2014 implemented the comma + `encodeValuesOnly` path differently (joining before encoding) and are not affected. Empirically verified across released versions.\u003c/p\u003e\u003cp\u003e### Impact\u003c/p\u003e\u003cp\u003eApplication code that calls `qs.stringify` with both `arrayFormat: \u0027comma\u0027` 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\u0027s 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.\u003c/p\u003e\u003cp\u003eThe 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`).\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-476\", \"description\": \"CWE-476 NULL Pointer Dereference\"}]}], \"providerMetadata\": {\"orgId\": \"7ffcee3d-2c14-4c3e-b844-86c6a321a158\", \"shortName\": \"harborist\", \"dateUpdated\": \"2026-05-16T23:21:16.035Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-8723\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-18T14:02:57.825Z\", \"dateReserved\": \"2026-05-16T06:26:43.607Z\", \"assignerOrgId\": \"7ffcee3d-2c14-4c3e-b844-86c6a321a158\", \"datePublished\": \"2026-05-16T23:21:16.035Z\", \"assignerShortName\": \"harborist\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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