CVE-2025-66457
HighCVSS 8.8Exploitation Probability (EPSS)
Elevated risk56th percentile - higher than 56% of all known CVEs
Summary
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, the cookie config is injected into the compiled route without first being sanitised. This issue is fixed in version 1.4.18.
Risk Assessment
An attacker with write access to the cookie config could execute arbitrary code, and when combined with GHSA-hxj9-33pp-j2cc, achieve a full RCE chain.
Recommendation
Upgrade Elysia to version 1.4.18 or later and secure write access to the cookie configuration.
Other vulnerabilities in Elysia
See all- CVE-2025-66456Critical
Elysia is a TypeScript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain a prototype pollution vulnerability in mergeDeep after merging results of two standard schema validations with the same key. Due to the ordering of merging, there must be an any type that is set as a standalone guard, to allow for the __proto__ prop to be merged. When combined with GHSA-8vch-m3f4-q8jf this allows for a full RCE by an attacker. This issue is fixed in version 1.4.17.
- CVE-2026-56669High
A vulnerability in Elysia prior to version 1.4.29 causes quadratic CPU workload growth when processing multipart/form-data with many unique key-value pairs. The use of getAll in data normalization leads to CPU exhaustion.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS