{"id":"CVE-2026-82562","summary":"qs.parse does not enforce arrayLimit on comma groups under bracket-push keys when throwOnLimitExceeded is set (incomplete fix for CVE-2026-2391)","details":"### Summary\n\n\n\nWhen `qs.parse` is called with `comma: true` and `throwOnLimitExceeded: true`, a comma-separated value under a bracket-push key (`a[]=1,2,3,4`) is split into an array without being compared against `arrayLimit`, while the same value under a flat key (`a=1,2,3,4`), an indexed key (`a[0]=`), a nested key (`a[b]=`), or a dotted key (`a.b=` with `allowDots`) throws the documented `RangeError`. A single parameter such as `a[]=1,2,2,...` therefore produces an inner array of arbitrary length even though the caller opted into the hard limit. This is the `[]=` key form that the fix for CVE-2026-2391 (qs 6.14.2) did not cover.\n\n\n\n### Details\n\n\n\nIn `lib/parse.js`, a comma-separated value under a `[]=` key is split and then wrapped as a single nested element (`val = [val]`, so that each `a[]=x,y` group counts as one element of the outer array). The `arrayLimit` check that 6.14.2 added for comma values runs after that wrap, so for `[]=` parts it only ever saw the wrapper of length 1. 6.15.3 added a pre-split comma count so that an oversized value throws before it is allocated, but gated it on an `isFlatArrayValue` flag that `parseValues` set to `false` for any part containing `[]=`, and did not pass it for object-valued input, so the gap remained.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require('qs');\n\n\n\nvar options = { comma: true, arrayLimit: 3, throwOnLimitExceeded: true };\n\n\n\nqs.parse('a=1,2,3,4', options);   // RangeError: Array limit exceeded. Only 3 elements allowed in an array.\n\n\n\nqs.parse('a[]=1,2,3,4', options); // { a: [ [ '1', '2', '3', '4' ] ] }  (no throw)\n\n\n\nqs.parse('a[]=' + '1,'.repeat(1000000) + '1', { comma: true, arrayLimit: 20, throwOnLimitExceeded: true });\n\n\n\n// no throw; a 1,000,001-element inner array is allocated\n\n\n\n```\n\n\n\n#### Fix\n\n\n\n`lib/parse.js`, applied in 8859c37 on `main` and released as v6.16.0: the `isFlatArrayValue` gate is removed, so every comma-split value is counted against `arrayLimit` before splitting regardless of key form. An in-limit group under `a[]=` still counts as one element of the outer array, and the default (`throwOnLimitExceeded: false`) path is unchanged.\n\n\n\n### Affected versions\n\n\n\n`\u003e=6.14.2 \u003c6.16.0`, fixed in v6.16.0.\n\n\n\nv6.14.2 introduced `arrayLimit` enforcement for comma values (the fix for CVE-2026-2391) but only for values not under a `[]=` key, and every release from v6.14.2 through v6.15.3 has the same gap. v6.14.0 and v6.14.1, where `throwOnLimitExceeded` exists but does not apply to any comma form, are covered by CVE-2026-2391 rather than this record. Earlier lines (6.7.x through 6.13.x) have `comma` but no `throwOnLimitExceeded`, so there is no hard cap on any comma path to bypass; releases before 6.7.0 have no `comma` option.\n\n\n\n### Impact\n\n\n\nAn unauthenticated attacker who can reach an application that parses untrusted query strings or urlencoded bodies with both `comma: true` and `throwOnLimitExceeded: true` (both non-default) can bypass the configured limit with a single `a[]=` parameter and force the parser to allocate an array proportional to the request size. The cost is strictly linear in the attacker-supplied bytes (about 0.1 microseconds and 6 to 7 retained bytes per input byte; the same out-of-memory threshold as the documented default `throwOnLimitExceeded: false` path), so a transport-layer request or body size limit bounds it completely (and node's default maximum HTTP header size of 16 KB already bounds the request line, so multi-megabyte payloads need a body parser). The impact is that an opt-in hard limit fails open on one key spelling, not unbounded allocation from a small input.","aliases":["GHSA-x5fp-wj9c-mxmx"],"modified":"2026-09-02T15:10:38.373081498Z","published":"2026-08-29T23:58:31.289Z","related":["GHSA-w7fw-mjwx-w883","GHSA-x5fp-wj9c-mxmx"],"database_specific":{"cna_assigner":"harborist","cwe_ids":["CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82562.json","unresolved_ranges":[{"extracted_events":[{"introduced":"6.14.2"},{"fixed":"6.16.0"}],"source":"AFFECTED_FIELD"}]},"references":[{"type":"WEB","url":"https://npmjs.com/qs"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82562.json"},{"type":"ADVISORY","url":"https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883"},{"type":"ADVISORY","url":"https://github.com/ljharb/qs/security/advisories/GHSA-x5fp-wj9c-mxmx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82562"},{"type":"FIX","url":"https://github.com/ljharb/qs/commit/8859c37470e11b42b547b275e4e9bd0bc8cc5464"},{"type":"PACKAGE","url":"https://github.com/ljharb/qs"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ljharb/qs","events":[{"introduced":"bdcf0c7f82387c18ac8fabfccd2f440645cef47b"},{"fixed":"18d085e919dae70c8f1b200ab99323058edab2c2"},{"introduced":"125e103b61f2bef245970f5a2a8dceffe5aab59a"},{"fixed":"5cf516c0dd557d85d5f18d4a916c96cd9cfc2305"},{"introduced":"0"},{"fixed":"125e103b61f2bef245970f5a2a8dceffe5aab59a"},{"fixed":"8859c37470e11b42b547b275e4e9bd0bc8cc5464"}],"database_specific":{"extracted_events":[{"introduced":"v6.14.2"},{"fixed":"v6.15.3"},{"introduced":"6.7.x"},{"fixed":"6.13.x"},{"introduced":"0"},{"fixed":"6.7.0"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["v6.15.3","v6.15.2","v6.15.1","v6.15.0","v6.14.2","v6.10.5","v6.11.2","v6.12.3","v6.12.2","v6.12.1","v6.12.0","v6.11.1","v6.11.0","v6.10.4","v6.10.3","v6.10.2","v6.10.1","v6.10.0","v6.9.6","v6.9.5","v6.9.4","v6.9.3","v6.9.2","v6.9.1","v6.9.0","v6.8.0","v6.7.0","v6.6.0","v6.5.2","v6.4.0","v6.5.1","v6.5.0","v6.3.1","v6.1.0","v6.2.1","v6.3.0","v5.2.0","v6.2.0","v6.0.2","v6.0.1","v6.0.0","v5.1.0","v5.0.0","v4.0.0","v3.1.0","v3.0.0","v2.4.2","v2.4.1","v2.4.0","v2.3.3","v2.3.2","v2.3.1","v2.3.0","v2.2.5","v2.2.4","v2.2.3","v2.2.2","v2.2.1","v2.2.0","v2.1.0","v2.0.0","v1.2.2","v1.2.1","v1.2.0","v1.1.0","v1.0.2","v1.0.1","v1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-82562.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}