CVE-2026-48819 Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-48819?
CVE-2026-48819 is a medium-severity vulnerability in hey-api openapi-ts, published on 17 Jul 2026.
Official description
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.
Weakness: CWE-1321
Which versions are affected by CVE-2026-48819?
2 open source packages ship an affected version, including @hey-api/openapi-ts.
| Package | Affected | Fixed in |
|---|---|---|
@hey-api/openapi-ts npm | All versions | 0.97.3 |
@hey-api/openapi-ts npm | All versions | 0.97.3 |
How do I fix CVE-2026-48819?
Upgrade @hey-api/openapi-ts to 0.97.3 or later.
Is CVE-2026-48819 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48819 exists.
Sources
Also known as GHSA-hhx9-57xq-r5rw.