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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-hxj9-33pp-j2cc Elysia vulnerable to prototype pollution with multiple standalone schema validation
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 10 Dec 2025 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Elysiajs
Elysiajs elysia
Vendors & Products Elysiajs
Elysiajs elysia

Tue, 09 Dec 2025 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 09 Dec 2025 19:45:00 +0000

Type Values Removed Values Added
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.
Title Elysia vulnerable to prototype pollution with multiple standalone schema validation
Weaknesses CWE-1321
References
Metrics cvssV4_0

{'score': 9.1, '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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-12-09T20:35:44.683Z

Reserved: 2025-12-01T22:51:54.580Z

Link: CVE-2025-66456

cve-icon Vulnrichment

Updated: 2025-12-09T20:11:40.823Z

cve-icon NVD

Status : Received

Published: 2025-12-09T20:15:54.760

Modified: 2025-12-09T21:16:00.030

Link: CVE-2025-66456

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2025-12-10T21:33:24Z

Weaknesses