{"id":"EUVD-2026-101710","revision":"bb3bbdbb5ccf4c0ba9910f9958f081e6","records":[{"revision":"bb3bbdbb5ccf4c0ba9910f9958f081e6","observedAt":"2026-10-30T01:56:00.18+00:00","statement":{"source":"euvd","id":"EUVD-2026-101710","aliases":["CVE-2026-110816","GHSA-6pq8-jhm2-2vcw"],"title":"### Summary","description":"### Summary\n\n\n\n`qs.stringify` with `arrayFormat: 'comma'` throws `TypeError: Cannot convert object to primitive value` when an array element cannot be coerced to a string, such as an object with an own non-callable `toString` (`{ \"toString\": \"x\" }`) or a null-prototype object. The comma format joins array elements with `Array.prototype.join` and, under `encodeValuesOnly`, first passes each element through `String()` in `utils.encode`; neither guards against an element whose string coercion fails.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the comma branch collapses the array with `obj.join(',')`. For an element whose own `toString` is not callable, `ToPrimitive` skips it, falls through to `Object.prototype.valueOf` (which returns the object itself), and throws. Under `encodeValuesOnly: true`, the same element first reaches `String(str)` in `utils.encode` (`lib/utils.js`) and throws there. Nested arrays (`{ \"a\": [[{ \"toString\": \"x\" }]] }`) throw the same way, through `Array.prototype.toString`. The `indices`, `brackets`, and `repeat` formats walk into object elements instead of coercing them, and are not affected.\n\n\n\nSuch elements can come from untrusted input. `JSON.parse` produces `{ \"a\": [{ \"toString\": \"x\" }] }` with no qs option involved. `qs.parse(\"a[0][toString]=x\", { allowPrototypes: true })` keeps the `toString` key, and `qs.parse(\"a[][b]=c\", { plainObjects: true })` produces a null-prototype element; the default parse options drop `toString` and produce ordinary objects, which do not throw. Express 4's default `query parser`, Express 5's `extended` query parser, and body-parser's `urlencoded({ extended: true })` all call `qs.parse` with `allowPrototypes: true`.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nqs.stringify(JSON.parse(\"{\\\"a\\\":[{\\\"toString\\\":\\\"x\\\"}]}\"), { arrayFormat: \"comma\" });\n\n\n\nqs.stringify(qs.parse(\"a[0][toString]=x\", { allowPrototypes: true }), { arrayFormat: \"comma\" });\n\n\n\nqs.stringify(qs.parse(\"a[][b]=c\", { plainObjects: true }), { arrayFormat: \"comma\", encodeValuesOnly: true });\n\n\n\n// TypeError: Cannot convert object to primitive value\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in a952e75 on `main` and released as v6.16.1: an element whose string coercion would fail is coerced to its primitive `valueOf`, if any, or else to `Object.prototype.toString`, so it renders as `[object Object]`, the same as any other object element already does under the comma format. Nested arrays are walked the way `join` walks them. Every input that did not previously throw serializes exactly as before, and a `toString` or `valueOf` that itself throws still propagates.\n\n\n\n### Affected versions\n\n\n\n`>=6.7.0 <6.16.1`, fixed in v6.16.1.\n\n\n\nThe `join` path was introduced with the comma format in b84acba and first shipped in v6.7.0; v6.6.x and earlier ignore `arrayFormat: 'comma'` and are not affected. The `encodeValuesOnly` `String()` site was introduced in 4c4b23d (v6.11.1); before that, the same input throws at `join`. Every release from v6.7.0 through v6.16.0 is affected.\n\n\n\n### Impact\n\n\n\nAn unauthenticated request can make any code path that re-serializes attacker-influenced data with `qs.stringify` and `arrayFormat: 'comma'` (for example, rebuilding a query string from `req.query` for a redirect or an upstream request, or serializing a parsed JSON body) throw synchronously. In a typical Node.js HTTP framework the throw is caught by the framework error boundary and the affected request returns a 500; the process survives and other requests are unaffected. Where the call runs outside an error boundary, such as an `async` Express 4 handler (where the throw becomes an unhandled promise rejection) or a bare `http` request handler, the process exits, so the impact in that case depends on the application error handling rather than on qs. The default `arrayFormat` (`indices`) is not affected.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"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":6.3,"severity":null}],"references":["https://github.com/ljharb/qs/security/advisories/GHSA-6pq8-jhm2-2vcw","https://github.com/ljharb/qs/commit/a952e7519338ef0cfb25694a2988848f93333727"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-101710","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Oct 14, 2026, 10:05:24 PM","dateUpdated":"Oct 16, 2026, 8:17:48 PM"},"relatedAdvisories":[{"id":"RHSA-2026:87077","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update","vulnerabilityIds":["CVE-2026-15577","CVE-2026-33374","CVE-2026-92539","CVE-2026-93294","CVE-2026-95502","CVE-2026-100347","CVE-2026-100348","CVE-2026-100349","CVE-2026-100351","CVE-2026-100352","CVE-2026-100353","CVE-2026-100354","CVE-2026-110816"]},{"id":"RHSA-2026:85266","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update","vulnerabilityIds":["CVE-2026-93450","CVE-2026-100347","CVE-2026-100348","CVE-2026-100349","CVE-2026-100351","CVE-2026-100352","CVE-2026-100353","CVE-2026-100354","CVE-2026-110816"]},{"id":"msrc_CVE-2026-110816","title":"qs.stringify with arrayFormat comma throws TypeError on array elements that cannot be coerced to a string","vulnerabilityIds":["CVE-2026-110816"]},{"id":"openSUSE-SU-2026:12261-1","title":"git-bug-0.11.0-3.1 on GA media","vulnerabilityIds":["CVE-2026-110095","CVE-2026-110180","CVE-2026-110306","CVE-2026-110725","CVE-2026-110816","CVE-2026-111756","CVE-2026-112085","CVE-2026-112366","CVE-2026-78659","CVE-2026-78660","CVE-2026-78663","CVE-2026-78669","CVE-2026-97032"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-101710","identifiers":["EUVD-2026-101710","CVE-2026-110816","GHSA-6pq8-jhm2-2vcw"]},"retained":false,"historicalAffected":[]}],"coverage":[]}