---
cve: "CVE-2025-66456"
severity: "CRITICAL"
cvss: 9.1
epss: "54%"
vendor: "elysiajs"
kev: false
exploited: false
published: "2025-12-09 20:15:54"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-07T06:56:25+02:00"
---

# CVE-2025-66456

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

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. To workaround, remove the `__proto__ key` from body.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- 428b9765af69739897b86c294563af8809dd40c3 (Commit)
- 26935bf76ebc43b4a43d48b173fc853de43bb51e (Commit)

## Referenzen

- <https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc>
- <https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf>
- <https://github.com/elysiajs/elysia/pull/1564>
- <https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e>
- <https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2025-66456) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_