CVE-2025-66457: Elysiajs Elysia

High severity, CVSS 8.8. EPSS: 0.8% chance of exploitation in the next 30 days.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.17 and below are subject to arbitrary code execution from cookie config. When dynamic cookies are enabled (e.g. there an existing cookie schema), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, but when combined with GHSA-hxj9-33pp-j2cc, it allows for a full RCE chain. An attack requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). This issue is fixed in version 1.4.18.

Affected products

• Elysiajs Elysia: before 1.4.18 (fixed in 1.4.18)

Published 2025-12-09. Last modified 2026-06-17.