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CVE-2026-48819— Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key

Quick assessment

Affected
hey-api openapi-ts
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Hey API Hey API是Hey API组织的一款TypeScript接口类型生成工具。 Hey API 0.97.3之前版本存在输入验证错误漏洞，该漏洞源于原型污染（CWE-1321），导致攻击者通过利用buildClientParams将包含$query___proto__的未知slot-prefixed键写入对应槽位，从而在for..in迭代中暴露继承的攻击者可控键。

CVSS 4.8 · Medium EPSS 0.27% · P19

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
hey-api openapi-ts < 0.97.3 affected
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I. Basic Information for CVE-2026-48819

Vulnerability Information
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Vulnerability Title
Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key
Source: CVE Program / CVE List V5
Vulnerability 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 $query___proto__ alongside a legitimate q field to set params.query through params["query"]["__proto__"] = value, call Object.setPrototypeOf(params.query, value), and expose inherited attacker-controlled keys during for..in iteration. This issue is fixed in version 0.97.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1321
Source: CVE Program / CVE List V5
Vulnerability Title
Hey API 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Hey API Hey API是Hey API组织的一款TypeScript接口类型生成工具。 Hey API 0.97.3之前版本存在输入验证错误漏洞，该漏洞源于原型污染（CWE-1321），导致攻击者通过利用buildClientParams将包含$query___proto__的未知slot-prefixed键写入对应槽位，从而在for..in迭代中暴露继承的攻击者可控键。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
hey-api openapi-ts < 0.97.3 -

II. Public POCs for CVE-2026-48819

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III. Intelligence Information for CVE-2026-48819

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Patches & Fixes for CVE-2026-48819 (2)

Vendor Advisories for CVE-2026-48819 (1)

Vendor Pages for CVE-2026-48819 (1)

IV. Related Vulnerabilities

Same weakness: CWE-1321