CVE-2026-31865: medium-severity vulnerability in elysiajs elysia
Elysia Cookie Value Prototype Pollution
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.5epss 0.2%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Affected products
elysiajs · elysiaRelated CVEs — elysiajs elysia
In the same product, most dangerous first.
CVE-2025-66457HIGHElysia affected by arbitrary code injection through cookie configEPSS 0.9%CVE-2026-56669HIGHElysia: Inefficient Algorithmic Complexity and Interpretation ConflictEPSS 0.6%CVE-2025-66456CRITICALElysia vulnerable to prototype pollution with multiple standalone schema validationEPSS 0.6%CVE-2026-30837HIGHElysia has a string URL format redosEPSS 0.5%