CVE-2026-31865: Elysiajs Elysia

Medium severity, CVSS 5.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible.

Affected products

• Elysiajs Elysia: before 1.4.27 (fixed in 1.4.27)

Published 2026-03-18. Last modified 2026-06-17.