CVE-2026-61534

Yayson is a library for serializing and reading JSON API data in JavaScript. Prior to 4.3.0, Store and LegacyStore use attacker-controlled JSON:API type, id, and relationship names as keys in plain-object lookup tables in src/yayson/store.ts and src/yayson/legacy-store.ts. A document whose type is __proto__ causes model-cache writes to modify Object.prototype, with the attacker controlling the polluted property name through id and its value through attributes. The malicious type can also be supplied by an included resource, and LegacyStore is reachable when a configured types mapping resolves to __proto__. Unsafe relationship names including __proto__, constructor, and prototype provide additional document-derived member paths. The resulting process-wide prototype pollution can cause denial of service and logic corruption; authorization bypass or code execution depends on suitable gadgets in the consuming application. This issue is fixed in version 4.3.0.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/confetti/yayson/commit/e460162d5a3ebac86424bead7424957c36f8dff9
https://github.com/confetti/yayson/pull/111
https://github.com/confetti/yayson/releases/tag/v4.3.0
https://github.com/confetti/yayson/security/advisories/GHSA-325j-mg25-8q58
https://github.com/confetti/yayson/security/advisories/GHSA-325j-mg25-8q58

Configurations

No configuration.

History

No history.

Information

Published : 2026-09-14 16:17

Updated : 2026-09-14 20:16

NVD link : CVE-2026-61534

Mitre link : CVE-2026-61534

CVE.ORG link : CVE-2026-61534

JSON object : View

Products Affected

No product.

CWE

CWE-1321

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

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