What is CVE-2026-48819?

CVE-2026-48819 is a medium-severity vulnerability in Hey-Api Openapi-Ts, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 4.8/10. Published 2026-07-17.

How severe is CVE-2026-48819?

Medium severity. CVSS v3 base score is 4.8 out of 10.

Prototype Pollution in Hey-Api Openapi-Ts

CVE-2026-48819

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.

Vulnerability class: Prototype Pollution

EPSS: 0.004 (28.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.

Affected products

Hey-api Openapi-ts — versions < 0.97.3

Weakness classification (CWE)

CWE-1321 — Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

References

security-advisories@github.com (x_refsource_CONFIRM)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-48819?: CVE-2026-48819 is a medium-severity vulnerability in Hey-Api Openapi-Ts, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 4.8/10. Published 2026-07-17.
How severe is CVE-2026-48819?: Medium severity. CVSS v3 base score is 4.8 out of 10.