{"id":"CVE-2025-66456","state":"PUBLISHED","title":"Elysia vulnerable to prototype pollution with multiple standalone schema validation","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.","publishedAt":"2025-12-09T19:43:10.252Z","updatedAt":"2025-12-09T20:35:44.683Z","severity":{"score":9.1,"label":"Critical","version":"4.0","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","source":"GitHub_M"},"assigner":"GitHub_M","products":["elysiajs elysia"],"affected":[{"vendor":"elysiajs","product":"elysia","versions":[{"version":">= 1.4.0, < 1.4.17","status":"affected"}]}],"references":["https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","https://github.com/elysiajs/elysia/pull/1564","https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e","https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e"],"weaknesses":["CWE-1321"],"ingestedAt":"2026-10-29T20:09:56.034Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/66xxx/CVE-2025-66456.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-66456","state":"PUBLISHED","datePublished":"2025-12-09T19:43:10.252Z","dateUpdated":"2025-12-09T20:35:44.683Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2025-12-01T22:51:54.580Z"},"containers":{"cna":{"title":"Elysia vulnerable to prototype pollution with multiple standalone schema validation","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"elysiajs","product":"elysia","versions":[{"version":">= 1.4.0, < 1.4.17","status":"affected"}]}],"references":[{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","name":"https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","name":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","tags":["x_refsource_MISC"]},{"url":"https://github.com/elysiajs/elysia/pull/1564","name":"https://github.com/elysiajs/elysia/pull/1564","tags":["x_refsource_MISC"]},{"url":"https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e","name":"https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e","tags":["x_refsource_MISC"]},{"url":"https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e","name":"https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1321","lang":"en","description":"CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2025-12-09T19:43:10.252Z"},"source":{"advisory":"GHSA-hxj9-33pp-j2cc","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc","tags":["exploit"]},{"url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2025-12-09T20:11:35.267669Z","id":"CVE-2025-66456","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-12-09T20:35:44.683Z"}}]}}}