ubuntu-cve-2026-82417
Vulnerability from osv_ubuntu
Published
2026-08-30 00:16
Modified
2026-09-02 16:28
Summary
Details
Summary qs.stringify throws a TypeError when it serializes an object whose own constructor property has a truthy, non-callable isBuffer member. utils.isBuffer duck-types buffers by calling obj.constructor.isBuffer(obj) after checking only that the property is truthy, so a value such as { constructor: { isBuffer: "x" } } makes the call throw TypeError: obj.constructor.isBuffer is not a function. ### Details lib/stringify.js:127 calls utils.isBuffer on every non-primitive value it serializes. utils.isBuffer (lib/utils.js:332) reads obj.constructor.isBuffer and invokes it without verifying that it is a function. constructor and isBuffer are ordinary property names, so any object carrying them as own properties reaches the unchecked call. Such an object can be built from untrusted input. qs.parse("x[constructor][isBuffer]=y", { plainObjects: true }) or { allowPrototypes: true } keeps the constructor key as an own property (the default parse options drop it), and JSON.parse("{\"a\":{\"constructor\":{\"isBuffer\":\"x\"}}}") produces the same shape with no qs option involved. Express 4 with its default query parser setting and body-parser with extended: true both call qs.parse with allowPrototypes: true, so on those stacks req.query and req.body can carry the shape directly. #### PoC js var qs = require("qs"); qs.stringify(qs.parse("x[constructor][isBuffer]=y", { plainObjects: true })); qs.stringify(JSON.parse("{\"a\":{\"constructor\":{\"isBuffer\":\"x\"}}}")); // TypeError: obj.constructor.isBuffer is not a function // at Object.isBuffer (lib/utils.js:332:78) // at stringify (lib/stringify.js:127:45) #### Fix lib/utils.js, applied in e83d321 on main and released as v6.16.0: diff - return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj)); + return !!(obj.constructor && typeof obj.constructor.isBuffer === "function" && obj.constructor.isBuffer(obj)); Real Buffer, safer-buffer, and browserify buffer polyfill instances serialize exactly as before; only the throw is removed. ### Affected versions >=2.2.5 <6.16.0, fixed in v6.16.0. The unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used Buffer.isBuffer and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call. ### Impact An unauthenticated request can make any code path that re-serializes attacker-influenced data with qs.stringify (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 background job, the process exits, so the impact in that case depends on the application error handling rather than on qs.
Severity
5.3 (Medium)
N/A (UNKNOWN)
References
{
"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 `qs.stringify` throws a `TypeError` when it serializes an object whose own `constructor` property has a truthy, non-callable `isBuffer` member. `utils.isBuffer` duck-types buffers by calling `obj.constructor.isBuffer(obj)` after checking only that the property is truthy, so a value such as `{ constructor: { isBuffer: \"x\" } }` makes the call throw `TypeError: obj.constructor.isBuffer is not a function`. ### Details `lib/stringify.js:127` calls `utils.isBuffer` on every non-primitive value it serializes. `utils.isBuffer` (`lib/utils.js:332`) reads `obj.constructor.isBuffer` and invokes it without verifying that it is a function. `constructor` and `isBuffer` are ordinary property names, so any object carrying them as own properties reaches the unchecked call. Such an object can be built from untrusted input. `qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true })` or `{ allowPrototypes: true }` keeps the `constructor` key as an own property (the default parse options drop it), and `JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\")` produces the same shape with no qs option involved. Express 4 with its default `query parser` setting and body-parser with `extended: true` both call `qs.parse` with `allowPrototypes: true`, so on those stacks `req.query` and `req.body` can carry the shape directly. #### PoC ```js var qs = require(\"qs\"); qs.stringify(qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true })); qs.stringify(JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\")); // TypeError: obj.constructor.isBuffer is not a function // at Object.isBuffer (lib/utils.js:332:78) // at stringify (lib/stringify.js:127:45) ``` #### Fix `lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0: ```diff - return !!(obj.constructor \u0026\u0026 obj.constructor.isBuffer \u0026\u0026 obj.constructor.isBuffer(obj)); + return !!(obj.constructor \u0026\u0026 typeof obj.constructor.isBuffer === \"function\" \u0026\u0026 obj.constructor.isBuffer(obj)); ``` Real `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed. ### Affected versions `\u003e=2.2.5 \u003c6.16.0`, fixed in v6.16.0. The unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used `Buffer.isBuffer` and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call. ### Impact An unauthenticated request can make any code path that re-serializes attacker-influenced data with `qs.stringify` (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 background job, the process exits, so the impact in that case depends on the application error handling rather than on qs.",
"id": "UBUNTU-CVE-2026-82417",
"modified": "2026-09-02T16:28:28Z",
"published": "2026-08-30T00:16:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-82417"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-82417"
},
{
"type": "REPORT",
"url": "https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g"
},
{
"type": "REPORT",
"url": "https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/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-2026-82417"
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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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
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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.
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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