Vulnerability-Lookup

CVE-2026-82417 (GCVE-0-2026-82417)

Vulnerability from cvelistv5 – Published: 2026-08-29 23:51 – Updated: 2026-08-29 23:51

Title

qs.stringify throws TypeError on objects with a non-callable constructor.isBuffer property

Summary

### 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)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

6.3 (Medium)


                        
                          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

CWE

CWE-248 - Uncaught Exception
CWE-703 - Improper Check or Handling of Exceptional Conditions

Assigner

harborist redhat root

References

2 references

URL	Tags
https://github.com/ljharb/qs/security/advisories/…	vendor-advisory
https://github.com/ljharb/qs/commit/e83d321ffafb3…	patch

Impacted products

1 product

Vendor	Product	Version	CPE status
ljharb	qs	Affected: 2.2.5 , < 6.16.0 (semver)	guessed

Credits

waydeshi ljharb

Show details on NVD website

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{
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    "cna": {
      "affected": [
        {
          "collectionURL": "https://npmjs.com/qs",
          "defaultStatus": "unaffected",
          "packageName": "qs",
          "product": "qs",
          "repo": "https://github.com/ljharb/qs",
          "vendor": "ljharb",
          "versions": [
            {
              "lessThan": "6.16.0",
              "status": "affected",
              "version": "2.2.5",
              "versionType": "semver"
            }
          ]
        }
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      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "waydeshi"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "ljharb"
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      ],
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              "value": "\u003cp\u003e### Summary\u003c/p\u003e\u003cp\u003e`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`.\u003c/p\u003e\u003cp\u003e### Details\u003c/p\u003e\u003cp\u003e`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.\u003c/p\u003e\u003cp\u003eSuch 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.\u003c/p\u003e\u003cp\u003e#### PoC\u003c/p\u003e\u003cp\u003e```js\u003c/p\u003e\u003cp\u003evar qs = require(\"qs\");\u003c/p\u003e\u003cp\u003eqs.stringify(qs.parse(\"x[constructor][isBuffer]=y\", { plainObjects: true }));\u003c/p\u003e\u003cp\u003eqs.stringify(JSON.parse(\"{\\\"a\\\":{\\\"constructor\\\":{\\\"isBuffer\\\":\\\"x\\\"}}}\"));\u003c/p\u003e\u003cp\u003e// TypeError: obj.constructor.isBuffer is not a function\u003c/p\u003e\u003cp\u003e//     at Object.isBuffer (lib/utils.js:332:78)\u003c/p\u003e\u003cp\u003e//     at stringify (lib/stringify.js:127:45)\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003e#### Fix\u003c/p\u003e\u003cp\u003e`lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0:\u003c/p\u003e\u003cp\u003e```diff\u003c/p\u003e\u003cp\u003e- return !!(obj.constructor \u0026amp;\u0026amp; obj.constructor.isBuffer \u0026amp;\u0026amp; obj.constructor.isBuffer(obj));\u003c/p\u003e\u003cp\u003e+ return !!(obj.constructor \u0026amp;\u0026amp; typeof obj.constructor.isBuffer === \"function\" \u0026amp;\u0026amp; obj.constructor.isBuffer(obj));\u003c/p\u003e\u003cp\u003e```\u003c/p\u003e\u003cp\u003eReal `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed.\u003c/p\u003e\u003cp\u003e### Affected versions\u003c/p\u003e\u003cp\u003e`\u0026gt;=2.2.5 \u0026lt;6.16.0`, fixed in v6.16.0.\u003c/p\u003e\u003cp\u003eThe 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.\u003c/p\u003e\u003cp\u003e### Impact\u003c/p\u003e\u003cp\u003eAn 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.\u003c/p\u003e"
            }
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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 \u0026\u0026 obj.constructor.isBuffer \u0026\u0026 obj.constructor.isBuffer(obj));\n\n\n\n+ return !!(obj.constructor \u0026\u0026 typeof obj.constructor.isBuffer === \"function\" \u0026\u0026 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`\u003e=2.2.5 \u003c6.16.0`, 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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            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
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            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
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              "type": "CWE"
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        "dateUpdated": "2026-08-29T23:51:27.634Z",
        "orgId": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
        "shortName": "harborist"
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      "references": [
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          "tags": [
            "vendor-advisory"
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          "url": "https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6"
        }
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              "value": "\u003cp\u003eUpgrade to qs 6.16.0 or later.\u003c/p\u003e"
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          "value": "Upgrade to qs 6.16.0 or later."
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      "source": {
        "discovery": "EXTERNAL"
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              "value": "\u003cp\u003ePass 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`.\u003c/p\u003e"
            }
          ],
          "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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    "assignerShortName": "harborist",
    "cveId": "CVE-2026-82417",
    "datePublished": "2026-08-29T23:51:27.634Z",
    "dateReserved": "2026-08-28T23:08:00.460Z",
    "dateUpdated": "2026-08-29T23:51:27.634Z",
    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-82417\",\"sourceIdentifier\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\",\"published\":\"2026-08-30T00:16:34.657\",\"lastModified\":\"2026-08-30T00:16:34.657\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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 \u0026\u0026 obj.constructor.isBuffer \u0026\u0026 obj.constructor.isBuffer(obj));\\n\\n\\n\\n+ return !!(obj.constructor \u0026\u0026 typeof obj.constructor.isBuffer === \\\"function\\\" \u0026\u0026 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`\u003e=2.2.5 \u003c6.16.0`, 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.\"}],\"affected\":[{\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\",\"affectedData\":[{\"vendor\":\"ljharb\",\"product\":\"qs\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://npmjs.com/qs\",\"packageName\":\"qs\",\"repo\":\"https://github.com/ljharb/qs\",\"versions\":[{\"version\":\"2.2.5\",\"lessThan\":\"6.16.0\",\"versionType\":\"semver\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"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/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\",\"baseScore\":6.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"LOW\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"cvssMetricV31\":[{\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-248\"},{\"lang\":\"en\",\"value\":\"CWE-703\"}]}],\"references\":[{\"url\":\"https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6\",\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\"},{\"url\":\"https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g\",\"source\":\"7ffcee3d-2c14-4c3e-b844-86c6a321a158\"}]}}"
  }
}

FKIE_CVE-2026-82417

Vulnerability from fkie_nvd - Published: 2026-08-30 00:16 - Updated: 2026-08-30 00:16

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Summary

References

	URL	Tags
	7ffcee3d-2c14-4c3e-b844-86c6a321a158	https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6
	7ffcee3d-2c14-4c3e-b844-86c6a321a158	https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://npmjs.com/qs",
          "defaultStatus": "unaffected",
          "packageName": "qs",
          "product": "qs",
          "repo": "https://github.com/ljharb/qs",
          "vendor": "ljharb",
          "versions": [
            {
              "lessThan": "6.16.0",
              "status": "affected",
              "version": "2.2.5",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "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 \u0026\u0026 obj.constructor.isBuffer \u0026\u0026 obj.constructor.isBuffer(obj));\n\n\n\n+ return !!(obj.constructor \u0026\u0026 typeof obj.constructor.isBuffer === \"function\" \u0026\u0026 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`\u003e=2.2.5 \u003c6.16.0`, 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."
    }
  ],
  "id": "CVE-2026-82417",
  "lastModified": "2026-08-30T00:16:34.657",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
        "type": "Secondary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "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/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",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-30T00:16:34.657",
  "references": [
    {
      "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
      "url": "https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6"
    },
    {
      "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
      "url": "https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g"
    }
  ],
  "sourceIdentifier": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-248"
        },
        {
          "lang": "en",
          "value": "CWE-703"
        }
      ],
      "source": "7ffcee3d-2c14-4c3e-b844-86c6a321a158",
      "type": "Secondary"
    }
  ]
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

CVE-2026-82417 (GCVE-0-2026-82417)

FKIE_CVE-2026-82417

Tags

Sightings

Nomenclature