--- id: CVE-2026-82417 title: >- ### Summary `qs.stringify` throws a `TypeError` when it serializes an object whose own `constructor` property has a truthy, non-callable `isBuffer` member 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)`… severity: medium cvss: 5.3 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L' cwe: - CWE-248 - CWE-703 - CWE-1287 published: '2026-08-30' updated: '2026-08-30' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-82417' references: - url: >- https://github.com/ljharb/qs/commit/e83d321ffafb38cf210683ac31714fce6ce1c6c6 label: 7ffcee3d-2c14-4c3e-b844-86c6a321a158 - url: 'https://github.com/ljharb/qs/security/advisories/GHSA-4mjr-xmp4-gh2g' label: 7ffcee3d-2c14-4c3e-b844-86c6a321a158 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-82417.json - url: 'https://access.redhat.com/security/cve/CVE-2026-82417' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2525936' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-82417' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-82417' - url: 'https://access.redhat.com/errata/RHSA-2026:62544' - url: 'https://access.redhat.com/errata/RHSA-2026:63164' - url: 'https://access.redhat.com/errata/RHSA-2026:67711' - url: 'https://access.redhat.com/errata/RHSA-2026:67714' - url: 'https://access.redhat.com/errata/RHSA-2026:68681' - url: 'https://access.redhat.com/errata/RHSA-2026:67724' - url: 'https://access.redhat.com/errata/RHSA-2026:69255' - url: 'https://access.redhat.com/errata/RHSA-2026:68766' - url: 'https://access.redhat.com/errata/RHSA-2026:68747' - url: 'https://access.redhat.com/errata/RHSA-2026:69289' - url: 'https://access.redhat.com/errata/RHSA-2026:71210' - url: 'https://access.redhat.com/errata/RHSA-2026:71179' - url: 'https://access.redhat.com/errata/RHSA-2026:68552' tags: - nvd - csaf - vex - red-hat - score-dispute ingestedAt: '2026-08-30T13:53:03.130Z' epss: 0.00418 epssPercentile: 0.33461 vendor: Red Hat product: Red Hat Enterprise Linux 9 affected: - cost_management_on_premise - cryostat 4 - migration_toolkit_for_applications 8 - migration_toolkit_for_containers - node_healthcheck_operator - openshift_lightspeed - openshift_pipelines - openshift_serverless - advanced_cluster_management_for_kubernetes 2 - advanced_cluster_security 4 - ansible_automation_platform 2 - build_of_podman_desktop - ceph_storage 4 - ceph_storage 6 - ceph_storage 7 - ceph_storage 8 - ceph_storage 9 - connectivity_link 1 - data_grid 8 - developer_hub - discovery 2 - enterprise_linux 10 - enterprise_linux 7 - enterprise_linux 8 - enterprise_linux 9 - enterprise_linux_ai_rhel_ai 3 - fuse 7 - hardened_images - jboss_enterprise_application_platform 7 - openshift_ai_rhoai - openshift_container_platform 4 - openshift_data_foundation 4 - openshift_dev_spaces - openshift_gitops - quay 3 - satellite 6 - trusted_artifact_signer - trusted_profile_analyzer - secrets_management_console_for_red_hat_openshift - self_service_automation_portal 2 patched: - hardened_images scores: nvd: 5.3 vendor: 7.5 --- ## Overview ### 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. ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **RHSA-2026:62544** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:62544) - **RHSA-2026:63164** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:63164) - **Red Hat VEX** · Important · affected: Ansible Automation Orchestrator 2026, Cost Management On Premise, Cryostat 4, Node HealthCheck Operator, OpenShift Lightspeed, OpenShift Pipelines, … · no fix planned: Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux 10, Red Hat Fuse 7, Red Hat Hardened Images, … · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-82417.json) - **RHSA-2026:67711** · Red Hat · fixed in: Red Hat Advanced Cluster Security for Kubernetes 4.10 · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67711) - **RHSA-2026:67714** · Red Hat · fixed in: Red Hat Advanced Cluster Security for Kubernetes 4.11 · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67714) - **RHSA-2026:68681** · Red Hat · fixed in: Red Hat Migration Toolkit 1.8 · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:68681) - **RHSA-2026:67724** · Red Hat · fixed in: Red Hat Migration Toolkit for Applications 8.2 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67724) - **RHSA-2026:69255** · Red Hat · fixed in: Red Hat Quay 3.16 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69255) - **RHSA-2026:68766** · Red Hat · fixed in: Red Hat Satellite 6.18 · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:68766) - **RHSA-2026:68747** · Red Hat · fixed in: Red Hat Satellite 6.19 · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:68747) - **RHSA-2026:69289** · Red Hat · fixed in: Red Hat Discovery 2 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69289) - **RHSA-2026:71210** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.5 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71210) - **RHSA-2026:71179** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.6 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71179) - **RHSA-2026:68552** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.22 · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:68552)