{"cve":"CVE-2025-66456","nvd":{"published":"2025-12-09T20:15:54.760","modified":"2026-10-14T21:10:00.183","status":"Analyzed","description":"Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain a prototype pollution vulnerability in `mergeDeep` after merging results of two standard schema validations with the same key. Due to the ordering of merging, there must be an any type that is set as a standalone guard, to allow for the `__proto__ prop` to be merged. When combined with GHSA-8vch-m3f4-q8jf this allows for a full RCE by an attacker. This issue is fixed in version 1.4.17. To workaround, remove the `__proto__ key` from body.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","score":9.1},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-1321"],"references":["https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e","https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e","https://github.com/elysiajs/elysia/pull/1564","https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc"],"products":["elysiajs:elysia"],"source":"nvd","synced_at":"2026-10-19T22:16:40.427100871+00:00"},"epss":{"cve":"CVE-2025-66456","score":0.0056,"percentile":0.46353,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-hxj9-33pp-j2cc","url":"https://osv.dev/vulnerability/GHSA-hxj9-33pp-j2cc","summary":"Elysia vulnerable to prototype pollution with multiple standalone schema validation","modified":"2026-02-04T03:31:17.532002Z","packages":[{"ecosystem":"npm","name":"elysia","purl":"pkg:npm/elysia","ranges":[">=1.4.0 <1.4.17"],"fixed":["1.4.17"]}]}],"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."]}