CVE-2025-66456

CRITICAL EPSS 37.4%
Published Dec 9, 20256mo ago · Modified Jun 17, 20262w ago
9.1 CVSS 4.0
Critical
Find Similar
Published Dec 9, 2025 6mo ago
Last Modified Jun 17, 2026 2w ago

Description

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 Details

Base Score
9.1
Exploitability
—
Impact
—
Vector string
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
37.4% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-1321

Affected Products 1

VendorProductVersionRange
elysiajselysia*≥1.4.0  –  <1.4.17

References 5

  • github.com https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e
    Patch
  • github.com https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e
    Patch
  • github.com https://github.com/elysiajs/elysia/pull/1564
    Issue TrackingPatch
  • github.com https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf
    Not Applicable
  • github.com https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc
    ExploitPatchVendor Advisory

Remediation

  • github.com https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e
    Patch
  • github.com https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e
    Patch
  • github.com https://github.com/elysiajs/elysia/pull/1564
    Issue TrackingPatch
  • github.com https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc
    ExploitPatchVendor Advisory