{"id":"CVE-2025-66456","title":"Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication","summary":"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 result…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-1321"],"vendor":"elysiajs","product":"elysia","affected":["elysia >= 1.4.0, < 1.4.17"],"patched":["elysia 1.4.17"],"published":"2025-12-09","updated":"2026-10-14","sourceUpdated":"2026-10-14T21:10:00.183","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-66456","references":[{"url":"https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e","label":"security-advisories@github.com"},{"url":"https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e","label":"security-advisories@github.com"},{"url":"https://github.com/elysiajs/elysia/pull/1564","label":"security-advisories@github.com"},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","label":"security-advisories@github.com"},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","label":"security-advisories@github.com"},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd"],"epss":0.0056,"epssPercentile":0.45287,"ingestedAt":"2026-10-14T21:57:04.770Z","slug":"CVE-2025-66456","body":"## Overview\n\nElysia 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.\n\n## Affected\n\n- `elysia >= 1.4.0, < 1.4.17`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `elysia 1.4.17`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}