CVE-2026-56669 Elysia: Inefficient Algorithmic Complexity and Interpretation Conflict
Attackers can cause CPU exhaustion in Elysia applications by sending multipart requests with many unique keys, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-56669?
CVE-2026-56669 is a high-severity denial of service vulnerability in elysiajs elysia, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to 1.4.29, Elysia uses getAll in form data normalization for multipart/form-data endpoints, causing the amount of work to grow quadratically with the number of unique key-value pairs and allowing CPU exhaustion. This issue is fixed in version 1.4.29.
Which versions are affected by CVE-2026-56669?
2 open source packages ship an affected version, including elysia.
| Package | Affected | Fixed in |
|---|---|---|
elysia npm | All versions | 1.4.29 |
elysia npm | All versions | 1.4.29 |
How do I fix CVE-2026-56669?
Upgrade elysia to 1.4.29 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-56669 being exploited?
There is no known exploitation of CVE-2026-56669 in the wild and no public exploit code.
Sources
Also known as GHSA-9643-4qgh-g8mx.