CVE-2025-66456

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.

PUBLISHED Reserved 2025-12-01 | Published 2025-12-09 | Updated 2025-12-09 | Assigner GitHub_M

Problem types

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Product status

References

github.com/...elysia/security/advisories/GHSA-hxj9-33pp-j2cc exploit

github.com/...elysia/security/advisories/GHSA-8vch-m3f4-q8jf exploit

github.com/...elysia/security/advisories/GHSA-hxj9-33pp-j2cc

github.com/...elysia/security/advisories/GHSA-8vch-m3f4-q8jf

github.com/elysiajs/elysia/pull/1564

github.com/...ommit/26935bf76ebc43b4a43d48b173fc853de43bb51e

github.com/...ommit/3af978663e437dccc6c1a2a3aff4b74e1574849e

cve.org (CVE-2025-66456)

nvd.nist.gov (CVE-2025-66456)

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