RCE in Elysiajs Elysia
CVE-2025-66457
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.
Vulnerability class: RCE (Remote Code Execution)
EPSS: 0.007 (50.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Elysiajs Elysia — versions < 1.4.18
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Patch, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Not Applicable)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2025-66457?
- CVE-2025-66457 is a high-severity vulnerability in Elysiajs Elysia, classified under Code Injection. CVSS score: 8.8/10. Published 2025-12-09.
- How severe is CVE-2025-66457?
- High severity. CVSS v3 base score is 8.8 out of 10.