CVE-2026-48819: Hey-API Openapi-Ts

Medium severity, CVSS 4.8. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Hey-API Openapi-Ts: before 0.97.3 (fixed in 0.97.3)

Published 2026-07-17. Last modified 2026-07-23.