{"id":"CVE-2026-110910","aliases":["CLSA-2026-1793180904","DEBIAN-CVE-2026-110910","EUVD-2026-110630","GHSA-w4cr-vjpx-p82q","UBUNTU-CVE-2026-110910","openSUSE-SU-2026:12429-1"],"status":"published","title":"qs.stringify with allowEmptyArrays does not encode the keys of empty arrays, allowing query string parameter injection","description":"### Summary\n\n\n\n`qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nvar query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });\n\n\n\n// \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"\n\n\n\nqs.parse(query);\n\n\n\n// { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }\n\n\n\nqs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });\n\n\n\n// \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).\n\n\n\n### Affected versions\n\n\n\n- `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6\n\n\n\n- `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4\n\n\n\n- `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3\n\n\n\n- `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4\n\n\n\n- `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2\n\n\n\nv6.17.0 and later are not affected.\n\n\n\n`allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.\n\n\n\n### Impact\n\n\n\nAn application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00286,"percentile":0.21408,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-116"],"published":"2026-10-27T06:42:42Z","modified":"2026-11-06T17:27:15Z","fixes":[{"ecosystem":"TuxCare:npm","package":"qs","fixed_in":["6.15.3-tuxcare.4"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"TuxCare:npm","package":"qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.15.3-tuxcare.0"},{"fixed":"6.15.3-tuxcare.4"}]}],"versions":["6.15.3","6.15.3-tuxcare.1","6.15.3-tuxcare.2","6.15.3-tuxcare.3"]},{"source":"osv","ecosystem":"Debian:12","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.11.0+ds+~6.9.7-3","6.11.0+ds+~6.9.7-4","6.13.0+ds+~6.9.16-1","6.14.1+ds+~6.14.0-1","6.15.0+ds+~6.15.0-1","6.15.0+ds+~6.15.0-2","6.15.0+ds+~6.15.0-3","6.15.2+ds+~6.15.1-1","6.16.0+ds+~6.15.1-1"]},{"source":"osv","ecosystem":"Debian:13","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.13.0+ds+~6.9.16-1","6.14.1+ds+~6.14.0-1","6.15.0+ds+~6.15.0-1","6.15.0+ds+~6.15.0-2","6.15.0+ds+~6.15.0-3","6.15.2+ds+~6.15.1-1","6.16.0+ds+~6.15.1-1"]},{"source":"osv","ecosystem":"Debian:14","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.13.0+ds+~6.9.16-1","6.14.1+ds+~6.14.0-1","6.15.0+ds+~6.15.0-1","6.15.0+ds+~6.15.0-2","6.15.0+ds+~6.15.0-3","6.15.2+ds+~6.15.1-1","6.16.0+ds+~6.15.1-1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:14.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.4.2-1","0.6.5-1","0.6.5-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.4-1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.4-1","2.2.4-1ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.5.2-1","6.9.0+ds-1","6.9.1+ds-1","6.9.1+ds-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.9.4+ds-1","6.10.1+ds-1","6.10.2+ds+~6.9.7-1","6.10.3+ds+~6.9.7-1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.11.0+ds+~6.9.7-3","6.11.0+ds+~6.9.7-4"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.14.1+ds+~6.14.0-1","6.15.2+ds+~6.15.1-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"node-qs","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.13.0+ds+~6.9.16-1","6.14.1+ds+~6.14.0-1"]},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"git-bug","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.11.0-4.1"}]}],"bundled":3}],"products":[{"vendor":"ljharb","product":"qs"}],"references":[{"url":"https://github.com/ljharb/qs/security/advisories/GHSA-w4cr-vjpx-p82q","tags":["vendor-advisory","advisory","report"]},{"url":"https://github.com/ljharb/qs/commit/234d5051f5071efaa025a7ca9e4d34a56a460a1b","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/commit/6b8bf1a53d7b0c5e7e434eaae8e2c0cffd5c2492","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/commit/033526fc82f2e80a3d896df2bce9137e34cb5dc5","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/commit/f9dd4830cb922363822cdfdca2cceb3ed9792224","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/commit/ad445aa23e4c3a97394c3b9a5f9d7a7159eb1f17","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/commit/5d3b1b9ec6afd0cfc760c8e12862873789a32fc8","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/pull/561","tags":["patch","fix","report"]},{"url":"https://github.com/ljharb/qs/issues/626","tags":["issue-tracking","report"]},{"url":"https://npmjs.com/qs","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/110xxx/CVE-2026-110910.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-110910","tags":["advisory"]},{"url":"https://github.com/ljharb/qs","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-110910","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-110910","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-110910","tags":["report"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2026-110910","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-111181","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-114604","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2026-110910","title":"qs.stringify with allowEmptyArrays does not encode the keys of empty arrays, allowing query string parameter injection","description":"### Summary\n\n\n\n`qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nvar query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });\n\n\n\n// \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"\n\n\n\nqs.parse(query);\n\n\n\n// { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }\n\n\n\nqs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });\n\n\n\n// \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).\n\n\n\n### Affected versions\n\n\n\n- `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6\n\n\n\n- `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4\n\n\n\n- `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3\n\n\n\n- `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4\n\n\n\n- `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2\n\n\n\nv6.17.0 and later are not affected.\n\n\n\n`allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.\n\n\n\n### Impact\n\n\n\nAn application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T06:42:42.365Z","modified":"2026-11-04T15:01:07.679Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-116"],"updated_at":"2026-11-04T16:33:47.459854Z"}],"euvd":[{"id":"EUVD-2026-110630","description":"### Summary\n\n\n\n`qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nvar query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });\n\n\n\n// \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"\n\n\n\nqs.parse(query);\n\n\n\n// { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }\n\n\n\nqs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });\n\n\n\n// \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).\n\n\n\n### Affected versions\n\n\n\n- `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6\n\n\n\n- `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4\n\n\n\n- `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3\n\n\n\n- `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4\n\n\n\n- `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2\n\n\n\nv6.17.0 and later are not affected.\n\n\n\n`allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.\n\n\n\n### Impact\n\n\n\nAn application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T06:42:42Z","modified":"2026-11-04T15:01:07Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-04T16:10:35.925015Z"}],"nvd":[{"id":"CVE-2026-110910","description":"### Summary\n\n\n\n`qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nvar query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });\n\n\n\n// \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"\n\n\n\nqs.parse(query);\n\n\n\n// { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }\n\n\n\nqs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });\n\n\n\n// \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).\n\n\n\n### Affected versions\n\n\n\n- `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6\n\n\n\n- `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4\n\n\n\n- `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3\n\n\n\n- `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4\n\n\n\n- `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2\n\n\n\nv6.17.0 and later are not affected.\n\n\n\n`allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.\n\n\n\n### Impact\n\n\n\nAn application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T07:16:32.263Z","modified":"2026-11-04T15:17:27.123Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low","assessor":"secondary"}],"cwes":["CWE-116"],"updated_at":"2026-11-04T18:06:23.753671Z"}],"osv":[{"id":"CVE-2026-110910","title":"qs.stringify with allowEmptyArrays does not encode the keys of empty arrays, allowing query string parameter injection","description":"### Summary\n\n\n\n`qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.\n\n\n\n### Details\n\n\n\nIn `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nvar query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });\n\n\n\n// \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"\n\n\n\nqs.parse(query);\n\n\n\n// { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }\n\n\n\nqs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });\n\n\n\n// \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment\n\n\n\n```\n\n\n\n#### Fix\n\n\n\nApplied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).\n\n\n\n### Affected versions\n\n\n\n- `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6\n\n\n\n- `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4\n\n\n\n- `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3\n\n\n\n- `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4\n\n\n\n- `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2\n\n\n\nv6.17.0 and later are not affected.\n\n\n\n`allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.\n\n\n\n### Impact\n\n\n\nAn application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T06:42:42.365Z","modified":"2026-11-06T17:27:15.349632134Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-116"],"updated_at":"2026-11-06T18:04:15.404536Z"},{"id":"DEBIAN-CVE-2026-110910","description":"### Summary    `qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short.    ### Details    In `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected.    #### PoC    ```js    var qs = require(\"qs\");    var query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true });    // \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\"    qs.parse(query);    // { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] }    qs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true });    // \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment    ```    #### Fix    Applied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting).    ### Affected versions    - `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6    - `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4    - `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3    - `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4    - `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2    v6.17.0 and later are not affected.    `allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected.    ### Impact    An application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T07:16:32.263Z","modified":"2026-11-05T09:47:26.163152511Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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","level":"medium"}],"updated_at":"2026-11-05T13:31:49.170436Z"},{"id":"UBUNTU-CVE-2026-110910","description":"### Summary `qs.stringify` with `allowEmptyArrays: true` writes the key of an empty array without encoding it, even though keys are encoded by default. A key that contains `\u0026` (or the configured `delimiter`), `=`, or `#` therefore becomes query string syntax instead of data, so a caller-supplied key name can add parameters to the serialized query string, or cut it short. ### Details In `lib/stringify.js`, the `allowEmptyArrays` branch returns `adjustedPrefix + '[]'` early, before the code that passes every other key through `encoder` and `formatter`. So `{ \"x\u0026k=v\": [\"1\"] }` serializes as `x%26k%3Dv%5B0%5D=1`, but `{ \"x\u0026k=v\": [] }` serializes as `x\u0026k=v[]`. The early return applies at any depth (`{ \"a\": { \"b\u0026k=v\": [] } }` gives `a[b\u0026k=v][]`), under every `arrayFormat`, with `allowDots`, and with a custom `encoder`, which is never called for that key. With `encode: false` or `encodeValuesOnly: true`, keys are intentionally left unencoded on every path; those configurations are not affected. #### PoC ```js var qs = require(\"qs\"); var query = qs.stringify({ q: \"hi\", \"x\u0026apiKey=evil\u0026y\": [] }, { allowEmptyArrays: true }); // \"q=hi\u0026x\u0026apiKey=evil\u0026y[]\" qs.parse(query); // { q: \"hi\", x: \"\", apiKey: \"evil\", y: [\"\"] } qs.stringify({ \"x#\": [], z: \"1\" }, { allowEmptyArrays: true }); // \"x#[]\u0026z=1\": in a URL, everything after \"#\" becomes the fragment ``` #### Fix Applied in 234d505 on `main` and released as v6.17.0, and backported to v6.16.2, v6.15.4, v6.14.3, v6.13.4, and v6.12.6: the key of an empty array goes through `encoder` and `formatter` exactly as the key of any other value does, so `{ \"x\u0026apiKey=evil\u0026y\": [] }` now serializes as `x%26apiKey%3Devil%26y[]`. Keys that need no encoding serialize as before, with two exceptions that match every other path: the brackets of a nested key are now encoded (`a[b][]` becomes `a%5Bb%5D[]`, which `qs.parse` reads identically), and with `encodeDotInKeys`, a dot in the key becomes `%252E` instead of `%2E` (which `decodeDotInKeys` previously misread as nesting). ### Affected versions - `\u003e=6.12.0 \u003c6.12.6`, fixed in v6.12.6 - `\u003e=6.13.0 \u003c6.13.4`, fixed in v6.13.4 - `\u003e=6.14.0 \u003c6.14.3`, fixed in v6.14.3 - `\u003e=6.15.0 \u003c6.15.4`, fixed in v6.15.4 - `\u003e=6.16.0 \u003c6.16.2`, fixed in v6.16.2 v6.17.0 and later are not affected. `allowEmptyArrays` was introduced in f22b2bc and first shipped in v6.12.0, with this early return. Earlier versions have no `allowEmptyArrays` option and are not affected. ### Impact An application that passes an object whose key names come from untrusted input to `qs.stringify` with `allowEmptyArrays: true` (for example, to forward a parsed JSON body or user-selected fields to an upstream service) can have parameters injected into the resulting query string. The injected parameters are not keys of the object, so deleting or overwriting a key on the object (such as setting a trusted `apiKey` after copying the user's fields) does not remove them; whether the attacker's value or the application's wins depends on how the receiving side handles a duplicate parameter. A `#` in such a key ends the query string early when the result is placed in a URL. `allowEmptyArrays` is off by default, and only keys whose value (after any `filter`) is an empty array are affected.","status":"published","published":"2026-10-27T07:16:00Z","modified":"2026-11-05T04:42:42Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low"},{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-05T13:33:25.727744Z"},{"id":"CLSA-2026-1793180904","title":"TuxCare security update for qs (1 CVE)","description":"TuxCare rebuilt qs to address 1 CVE. Fixed in 6.15.3-tuxcare.4.","status":"published","published":"2026-10-28T09:48:24Z","modified":"2026-10-28T13:45:02.696059409Z","updated_at":"2026-11-02T15:43:55.34846Z"},{"id":"openSUSE-SU-2026:12429-1","title":"git-bug-0.11.0-4.1 on GA media","description":"These are all security issues fixed in the git-bug-0.11.0-4.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-11-05T00:00:00Z","modified":"2026-11-06T17:23:11.628955542Z","updated_at":"2026-11-06T18:05:03.243497Z"}]}}