UBUNTU-CVE-2026-82562 (CVE-2026-82562)
Vulnerability from osv_ubuntu – Published: 2026-08-30 01:20 – Updated: 2026-09-02 16:28 – Source website
VLAI
Details
Summary When 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. ### Details In 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. #### PoC js var qs = require('qs'); var options = { comma: true, arrayLimit: 3, throwOnLimitExceeded: true }; qs.parse('a=1,2,3,4', options); // RangeError: Array limit exceeded. Only 3 elements allowed in an array. qs.parse('a[]=1,2,3,4', options); // { a: [ [ '1', '2', '3', '4' ] ] } (no throw) qs.parse('a[]=' + '1,'.repeat(1000000) + '1', { comma: true, arrayLimit: 20, throwOnLimitExceeded: true }); // no throw; a 1,000,001-element inner array is allocated #### Fix 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. ### Affected versions >=6.14.2 <6.16.0, fixed in v6.16.0. v6.14.2 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. ### Impact An 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.
Severity
N/A (UNKNOWN)
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "0.6.5-1ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@0.6.5-1ubuntu0.1~esm1?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.4.2-1",
"0.6.5-1",
"0.6.5-1ubuntu0.1~esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "2.2.4-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@2.2.4-1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.2.4-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "2.2.4-1ubuntu1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@2.2.4-1ubuntu1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.2.4-1",
"2.2.4-1ubuntu1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "6.9.1+ds-1ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@6.9.1+ds-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"6.5.2-1",
"6.9.0+ds-1",
"6.9.1+ds-1",
"6.9.1+ds-1ubuntu0.1~esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "6.10.3+ds+~6.9.7-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@6.10.3+ds+~6.9.7-1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"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"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "6.11.0+ds+~6.9.7-4"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@6.11.0+ds+~6.9.7-4?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"6.11.0+ds+~6.9.7-3",
"6.11.0+ds+~6.9.7-4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-qs",
"binary_version": "6.14.1+ds+~6.14.0-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "node-qs",
"purl": "pkg:deb/ubuntu/node-qs@6.14.1+ds+~6.14.0-1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"6.13.0+ds+~6.9.16-1",
"6.14.1+ds+~6.14.0-1"
]
}
],
"aliases": [],
"details": "### Summary When `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. ### Details In `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. #### PoC ```js var qs = require(\u0027qs\u0027); var options = { comma: true, arrayLimit: 3, throwOnLimitExceeded: true }; qs.parse(\u0027a=1,2,3,4\u0027, options); // RangeError: Array limit exceeded. Only 3 elements allowed in an array. qs.parse(\u0027a[]=1,2,3,4\u0027, options); // { a: [ [ \u00271\u0027, \u00272\u0027, \u00273\u0027, \u00274\u0027 ] ] } (no throw) qs.parse(\u0027a[]=\u0027 + \u00271,\u0027.repeat(1000000) + \u00271\u0027, { comma: true, arrayLimit: 20, throwOnLimitExceeded: true }); // no throw; a 1,000,001-element inner array is allocated ``` #### Fix `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. ### Affected versions `\u003e=6.14.2 \u003c6.16.0`, fixed in v6.16.0. v6.14.2 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. ### Impact An 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\u0027s 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.",
"id": "UBUNTU-CVE-2026-82562",
"modified": "2026-09-02T16:28:28Z",
"published": "2026-08-30T01:20:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-82562"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-82562"
},
{
"type": "REPORT",
"url": "https://github.com/ljharb/qs/security/advisories/GHSA-x5fp-wj9c-mxmx"
},
{
"type": "REPORT",
"url": "https://github.com/ljharb/qs/commit/8859c37470e11b42b547b275e4e9bd0bc8cc5464"
},
{
"type": "REPORT",
"url": "https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
"type": "CVSS_V3"
},
{
"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",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-82562"
]
}
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Sightings
| Author | Source | Type | Date | Other |
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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