231 lines
16 KiB
JSON
231 lines
16 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-82417",
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"assignerOrgId": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
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"state": "PUBLISHED",
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"assignerShortName": "harborist",
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"dateReserved": "2026-08-28T23:08:00.460Z",
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"datePublished": "2026-08-29T23:51:27.634Z",
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"dateUpdated": "2026-08-31T17:08:24.074Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
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"shortName": "harborist",
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"dateUpdated": "2026-08-29T23:51:27.634Z"
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},
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"title": "qs.stringify throws TypeError on objects with a non-callable constructor.isBuffer property",
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"problemTypes": [
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{
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"descriptions": [
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{
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"lang": "en",
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"cweId": "CWE-248",
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"description": "CWE-248 Uncaught Exception",
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"type": "CWE"
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}
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]
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},
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{
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"descriptions": [
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{
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"lang": "en",
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"cweId": "CWE-703",
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"description": "CWE-703 Improper Check or Handling of Exceptional Conditions",
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"type": "CWE"
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}
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]
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}
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],
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"affected": [
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{
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"vendor": "ljharb",
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"product": "qs",
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"collectionURL": "https://npmjs.com/qs",
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"packageName": "qs",
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"repo": "https://github.com/ljharb/qs",
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"versions": [
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{
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"status": "affected",
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"version": "2.2.5",
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"lessThan": "6.16.0",
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"versionType": "semver"
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}
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],
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"defaultStatus": "unaffected"
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}
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],
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"descriptions": [
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{
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"lang": "en",
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"value": "### Summary\n\n\n\n`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`.\n\n\n\n### Details\n\n\n\n`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.\n\n\n\nSuch 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.\n\n\n\n#### PoC\n\n\n\n```js\n\n\n\nvar qs = require(\"qs\");\n\n\n\nqs.stringify(qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true }));\n\n\n\nqs.stringify(JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\"));\n\n\n\n// TypeError: obj.constructor.isBuffer is not a function\n\n\n\n// at Object.isBuffer (lib/utils.js:332:78)\n\n\n\n// at stringify (lib/stringify.js:127:45)\n\n\n\n```\n\n\n\n#### Fix\n\n\n\n`lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0:\n\n\n\n```diff\n\n\n\n- return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));\n\n\n\n+ return !!(obj.constructor && typeof obj.constructor.isBuffer === \"function\" && obj.constructor.isBuffer(obj));\n\n\n\n```\n\n\n\nReal `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed.\n\n\n\n### Affected versions\n\n\n\n`>=2.2.5 <6.16.0`, fixed in v6.16.0.\n\n\n\nThe 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.\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` (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.",
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"supportingMedia": [
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{
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"type": "text/html",
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"base64": false,
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"value": "<p>### Summary</p><p>`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`.</p><p>### Details</p><p>`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.</p><p>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.</p><p>#### PoC</p><p>```js</p><p>var qs = require(\"qs\");</p><p>qs.stringify(qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true }));</p><p>qs.stringify(JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\"));</p><p>// TypeError: obj.constructor.isBuffer is not a function</p><p>// at Object.isBuffer (lib/utils.js:332:78)</p><p>// at stringify (lib/stringify.js:127:45)</p><p>```</p><p>#### Fix</p><p>`lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0:</p><p>```diff</p><p>- return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));</p><p>+ return !!(obj.constructor && typeof obj.constructor.isBuffer === \"function\" && obj.constructor.isBuffer(obj));</p><p>```</p><p>Real `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed.</p><p>### Affected versions</p><p>`>=2.2.5 <6.16.0`, fixed in v6.16.0.</p><p>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.</p><p>### Impact</p><p>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.</p>"
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}
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]
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}
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],
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"references": [
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{
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"url": "https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g",
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"tags": [
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"vendor-advisory"
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]
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},
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{
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"url": "https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6",
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"tags": [
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"patch"
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]
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}
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],
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"metrics": [
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{
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"format": "CVSS",
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"scenarios": [
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{
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"lang": "en",
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"value": "GENERAL"
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}
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],
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"cvssV3_1": {
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"version": "3.1",
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"attackVector": "NETWORK",
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"attackComplexity": "LOW",
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"privilegesRequired": "NONE",
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"userInteraction": "NONE",
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"scope": "UNCHANGED",
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"confidentialityImpact": "NONE",
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"integrityImpact": "NONE",
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"availabilityImpact": "LOW",
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"baseSeverity": "MEDIUM",
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"baseScore": 5.3,
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
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}
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},
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{
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"format": "CVSS",
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"scenarios": [
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{
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"lang": "en",
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"value": "GENERAL"
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}
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],
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"cvssV4_0": {
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"attackVector": "NETWORK",
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"attackComplexity": "LOW",
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"attackRequirements": "PRESENT",
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"privilegesRequired": "NONE",
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"userInteraction": "NONE",
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"vulnConfidentialityImpact": "NONE",
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"subConfidentialityImpact": "NONE",
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"vulnIntegrityImpact": "NONE",
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"subIntegrityImpact": "NONE",
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"vulnAvailabilityImpact": "LOW",
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"subAvailabilityImpact": "NONE",
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"exploitMaturity": "NOT_DEFINED",
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"Safety": "NOT_DEFINED",
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"Automatable": "NOT_DEFINED",
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"Recovery": "NOT_DEFINED",
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"valueDensity": "NOT_DEFINED",
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"vulnerabilityResponseEffort": "NOT_DEFINED",
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"providerUrgency": "NOT_DEFINED",
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"version": "4.0",
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"baseSeverity": "MEDIUM",
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"baseScore": 6.3,
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"vectorString": "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"
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}
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}
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],
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"workarounds": [
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{
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"lang": "en",
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"value": "Pass a `filter` function to `qs.stringify` that drops values carrying an own `constructor` property; it runs before the `isBuffer` check. Alternatively, wrap `qs.stringify` calls on externally influenced objects in try/catch, and avoid `allowPrototypes: true` / `plainObjects: true` when parsed untrusted input is fed back into `qs.stringify`.",
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"supportingMedia": [
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{
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"type": "text/html",
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"base64": false,
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"value": "<p>Pass a `filter` function to `qs.stringify` that drops values carrying an own `constructor` property; it runs before the `isBuffer` check. Alternatively, wrap `qs.stringify` calls on externally influenced objects in try/catch, and avoid `allowPrototypes: true` / `plainObjects: true` when parsed untrusted input is fed back into `qs.stringify`.</p>"
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}
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]
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}
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],
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"solutions": [
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{
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"lang": "en",
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"value": "Upgrade to qs 6.16.0 or later.",
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"supportingMedia": [
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{
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"type": "text/html",
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"base64": false,
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"value": "<p>Upgrade to qs 6.16.0 or later.</p>"
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}
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]
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}
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],
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"credits": [
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{
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"lang": "en",
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"value": "waydeshi",
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"type": "finder"
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},
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{
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"lang": "en",
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"value": "ljharb",
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"type": "remediation developer"
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}
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],
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"source": {
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"discovery": "EXTERNAL"
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}
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},
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"adp": [
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{
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"references": [
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{
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"url": "https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g",
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"tags": [
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"exploit"
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]
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}
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],
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"metrics": [
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{
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"other": {
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"type": "ssvc",
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"content": {
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"timestamp": "2026-08-31T17:07:54.823942Z",
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"id": "CVE-2026-82417",
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"options": [
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{
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"Exploitation": "poc"
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},
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{
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"Automatable": "yes"
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},
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{
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"Technical Impact": "partial"
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}
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],
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"role": "CISA Coordinator",
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"version": "2.0.3"
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}
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}
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2026-08-31T17:08:24.074Z"
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}
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}
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]
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}
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} |