CVE-2026-48819 — Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key
Hey API is an ecosystem for turning API specifications into production-ready code. Prior to 0.97.3, dist/clients/core/params.ts ships a runtime template copied into generated SD…
Published: 2026-07-17 · CVSS: 4.8 · CVSS 3.1
Hey API is an ecosystem for turning API specifications into production-ready code. Prior to 0.97.3, dist/clients/core/params.ts ships a runtime template copied into generated SDKs as params.gen.ts, and buildClientParams writes unknown slot-prefixed keys such as $body_, $headers_, $path_, and $query_ directly to the corresponding slot, allowing $query___proto__ alongside a legitimate q field to set params.query through params["query"]["__proto__"] = value, call Object.setPrototypeOf(params.query, value), and expose inherited attacker-controlled keys during for..in iteration. This issue is fixed in version 0.97.3.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7