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CVE-2026-61534— Yayson: Prototype pollution in the Store/LegacyStore deserialization

Quick assessment

Affected
confetti yayson
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.

Yayson 是一个用于在 JavaScript 中序列化及读取 JSON API 数据的库。在 4.3.0 版本之前，Store 和 LegacyStore 在 和 中，将攻击者可控的 JSON:API 类型（type）、ID（id）和关联（relationship）名称作为键，用于普通对象查找表。若文档的 type 为 ，模型缓存写入操作将修改 ，攻击者可通过 id 控制被污染的属性名，并通过 attributes 控制其值。恶意 type 也可由包含的资源（included resource）提供；当配置的

CVSS 9.1 · Critical EPSS 0.78% · P54

Possible ATT&CK Techniques 1 AI

T1598 · Phishing for Information

Affected Version Matrix 1

VendorProduct Version RangeStatus
confetti yayson < 4.3.0 affected
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I. Basic Information for CVE-2026-61534

Vulnerability Information
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Vulnerability Title
Yayson: Prototype pollution in the Store/LegacyStore deserialization
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1321
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
confetti yayson < 4.3.0 -

II. Public POCs for CVE-2026-61534

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III. Intelligence Information for CVE-2026-61534

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Patches & Fixes for CVE-2026-61534 (2)

Vendor Advisories for CVE-2026-61534 (1)

Vendor Pages for CVE-2026-61534 (1)

IV. Related Vulnerabilities

Same weakness: CWE-1321

V. Comments for CVE-2026-61534

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