Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| hey-api | openapi-ts | before 0.97.3 | 0.97.3 | Patch available | CNA |
| — | @hey-api/openapi-ts (npm) | before 0.97.3 | 0.97.3 | Patch available | GHSA-hhx9-57xq-r5rw |
- openapi-ts Vendorhey-api Affected before 0.97.3 Fixed in 0.97.3 Patch available CNA
- @hey-api/openapi-ts (npm) Vendor— Affected before 0.97.3 Fixed in 0.97.3 Patch available GHSA-hhx9-57xq-r5rw
Remediation
- Fix · CNA openapi-ts (hey-api) Fixed in 0.97.3
- Fix · GHSA-hhx9-57xq-r5rw @hey-api/openapi-ts (npm) Fixed in 0.97.3 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-48819
- 2026-10-03 Alias added: GHSA-hhx9-57xq-r5rw
References
Other 6
- https://github.com/hey-api/hey-api/security/advisories/GHSA-hhx9-57xq-r5rw
- https://github.com/hey-api/hey-api/commit/023909137a15eff9c0263d3bcd116140076b214f
- https://github.com/hey-api/hey-api/commit/da321a1529eb3c90d2109da870f514b915a60169
- https://github.com/hey-api/hey-api/releases/tag/%40hey-api%2Fopenapi-ts%400.97.3
- https://github.com/hey-api/openapi-ts/security/advisories/GHSA-hhx9-57xq-r5rw
- https://github.com/hey-api/openapi-ts
Sources
- CVE-2026-48819 · CVE Program
- CVE-2026-48819 · NVD
- FIRST EPSS
- GHSA-hhx9-57xq-r5rw · GitHub Advisory Database · CC BY 4.0
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