CVE-2026-31865CWE-1321

Elysia Cookie Value Prototype Pollution

Medium · published March 18, 2026

CVSS v3.1
6.5
EPSS
0%
Percentile
26.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.5 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00345 · 26.8th percentile
Weakness
CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Published
2026-03-18T02:50Z
EPSS history
Timeline
  • 18 MAR 02:50Z
    Elysia Cookie Value Prototype Pollution
    cvelistv5