CVE-2025-66456

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 v3 9.8 CRITICAL

9.8^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e	Patch
https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e	Patch
https://github.com/elysiajs/elysia/pull/1564	Issue Tracking Patch
https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf	Not Applicable
https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc	Exploit Patch Vendor Advisory
https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf	Not Applicable
https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc	Exploit Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:elysiajs:elysia:*:*:*:*:*:node.js:*:*

History

No history.

Information

Published : 2025-12-09 20:15

Updated : 2025-12-17 14:30

NVD link : CVE-2025-66456

Mitre link : CVE-2025-66456

CVE.ORG link : CVE-2025-66456

JSON object : View

Products Affected

elysiajs

elysia

CWE

CWE-1321

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

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