What’s Vulnerable › Vulnerabilities

CVE-2025-66457: Elysia affected by arbitrary code injection through cookie config

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-12-09 · updated 2026-10-14
• Weakness: CWE-94

Description

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

How to fix

Upgrade to a fixed version: elysiajs elysia 1.4.18. Check the vendor advisory for mitigations.

References

• https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e
• https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e
• https://github.com/elysiajs/elysia/pull/1564
• https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf
• https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc
• https://github.com/sportshead/elysia-poc

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