{"cve":"CVE-2026-61534","nvd":{"published":"2026-09-14T16:17:16.847","modified":"2026-09-30T17:51:56.193","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","score":9.1},"cwes":["CWE-1321"],"references":["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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-61534","score":0.0084,"percentile":0.57593,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-325j-mg25-8q58","url":"https://osv.dev/vulnerability/GHSA-325j-mg25-8q58","summary":"yayson: Prototype pollution in Store/LegacyStore deserialization","modified":"2026-09-11T22:15:03.886098994Z","packages":[{"ecosystem":"npm","name":"yayson","purl":"pkg:npm/yayson","ranges":["<4.3.0"],"fixed":["4.3.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}