GitHub Advisoryadvisory · npm

GHSA-9643-4qgh-g8mx elysia has Inefficient Algorithmic Complexity and Interpretation Conflict

HIGH Published 2026-09-23 Modified 2026-09-23 Official page ↗
Aliases
CVE-2026-56669
Ecosystem
npm
Packages
elysia
Severity
High
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
CWE-407, CWE-436
Reviewed
2026-09-23

Affected packages

• npm elysia: < 1.4.29 → fixed in 1.4.29

Description

Elysia v1.4.28 is vulnerable to denial-of-service attacks due to CPU exhaustion in the form data normalization code. Elysia uses `getAll` to retrieve value from FormData. It is called directly relative to the total number of key-value pairs in the form data. The total amount of work the for loop has to do grows quadratically, so doubling the number of unique key-value pairs quadruples the amount of work. In the above PoC, each .getAll call scans through all of the `n` key-value pairs in the form data. Because there are `n` unique keys in the form data, there are .getAll calls, so in total the form data normalizer has to scan `n` x `n` key-value pairs. Impact Endpoints using `multipart/form-data` Patches 1.4.29 Workarounds no 100% confirm workaround beside updating the patch

Related

Alias · CVE (1)

  • CVE-2026-56669 Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. vulnerability

Weakness · CWE (2)

  • CWE-407 Inefficient Algorithmic Complexity weakness
  • CWE-436 Interpretation Conflict weakness

References