Threats affecting pkg:npm/elysiajs/elysia

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

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.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Prior to 1.4.26 , t.String({ format: 'url' }) is vulnerable to ReDoS. Repeating a partial url format (protocol and hostname) multiple times cause regex to slow down significantly. This vulnerability is fixed in 1.4.26.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.17 and below are subject to arbitrary code execution from cookie config. When dynamic cookies are enabled (e.g.there an existing cookie schema), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, but when combined with GHSA-hxj9-33pp-j2cc, it allows for a full RCE chain. An attack requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). This issue is fixed in version 1.4.18.

CVE-2025-66456 is a critical prototype pollution vulnerability in the Elysia Typescript framework versions 1.4.0 through 1.4.16. It arises from improper merging of schema validation results in the mergeDeep function, allowing an attacker to manipulate the __proto__ property. When combined with another vulnerability (GHSA-8vch-m3f4-q8jf), this can lead to full remote code execution (RCE) without authentication or user interaction. The vulnerability has a CVSS 4.0 score of 9.1, indicating high severity.