GitHub Advisoryadvisory · npm
GHSA-9643-4qgh-g8mx elysia has Inefficient Algorithmic Complexity and Interpretation Conflict
HIGH
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
References
- https://github.com/elysiajs/elysia/security/advisories/GHSA-9643-4qgh-g8mx web
- https://nvd.nist.gov/vuln/detail/CVE-2026-56669 advisory
- https://github.com/elysiajs/elysia/commit/8358ff9efbcedf9534995f5977f26b9ceab59329 web
- https://gist.github.com/jviide/ea040eabe7bac058326174e2cd42dfd9 web
- https://github.com/elysiajs/elysia package
- https://github.com/elysiajs/elysia/releases/tag/1.4.29 web