CVE-2026-48819: CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in hey-api openapi-ts
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.
AI Analysis
Technical Summary
Hey API's openapi-ts package versions before 0.97.3 contain a prototype pollution vulnerability (CWE-1321). The runtime template in dist/clients/core/params.ts, copied into generated SDKs as params.gen.ts, allows the buildClientParams function to write unknown slot-prefixed keys such as $query___proto__ directly to the corresponding parameter slot. This enables an attacker to set params.query.__proto__ to an arbitrary value, effectively modifying the prototype of the params.query object. As a result, inherited attacker-controlled keys can be exposed during for..in iteration. This vulnerability is resolved in version 0.97.3.
Potential Impact
An attacker can manipulate the prototype of parameter objects, potentially causing unexpected behavior in applications using the affected versions of openapi-ts. This may lead to exposure of attacker-controlled keys during object iteration, which could affect application logic relying on these parameters. The CVSS score of 4.8 indicates a medium impact with low confidentiality and integrity impact and no availability impact.
Mitigation Recommendations
Upgrade to hey-api openapi-ts version 0.97.3 or later, where this prototype pollution vulnerability is fixed. No other mitigation or temporary workaround is indicated.
CVE-2026-48819: CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in hey-api openapi-ts
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.
CVSS v3.1
Score 4.8medium
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Hey API's openapi-ts package versions before 0.97.3 contain a prototype pollution vulnerability (CWE-1321). The runtime template in dist/clients/core/params.ts, copied into generated SDKs as params.gen.ts, allows the buildClientParams function to write unknown slot-prefixed keys such as $query___proto__ directly to the corresponding parameter slot. This enables an attacker to set params.query.__proto__ to an arbitrary value, effectively modifying the prototype of the params.query object. As a result, inherited attacker-controlled keys can be exposed during for..in iteration. This vulnerability is resolved in version 0.97.3.
Potential Impact
An attacker can manipulate the prototype of parameter objects, potentially causing unexpected behavior in applications using the affected versions of openapi-ts. This may lead to exposure of attacker-controlled keys during object iteration, which could affect application logic relying on these parameters. The CVSS score of 4.8 indicates a medium impact with low confidentiality and integrity impact and no availability impact.
Mitigation Recommendations
Upgrade to hey-api openapi-ts version 0.97.3 or later, where this prototype pollution vulnerability is fixed. No other mitigation or temporary workaround is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-22T20:57:10.976Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a5b5eae2d1edb114c7fb31e
Added to database: 07/18/2026, 11:08:30 UTC
Last enriched: 07/25/2026, 22:48:38 UTC
Last updated: 08/29/2026, 10:52:09 UTC
Views: 69
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