Critical 9.8Published Dec 9, 2025

CVE-2025-66456Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication.

Updated under an hour ago (2026-10-19 09:50 UTC)

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Every CVE for elysiajs elysia

Exploited in the last 30 days

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: 9.8 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-1321
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Analyzed
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

elysiajs elysia elysiajs:elysia	from 1.4.0 before 1.4.17	NVD

References

https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51epatch
https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849epatch
https://github.com/elysiajs/elysia/pull/1564issue-tracking, patch
https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jfnot-applicable
https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2ccexploit, patch, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.