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.
Affected products
elysiajs: elysia
References7
- github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j… ExploitPatchVendor Advisory
- github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j… ExploitPatchVendor Advisory
- github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc8… Patch
- github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b… Patch
- github.com/elysiajs/elysia/pull/1564 Issue TrackingPatch
- github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q… Not Applicable
- github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q… Not Applicable
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 4.0
-
9.1
CRITICAL
Score source: CNA
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 - EPSS — exploit probability
- 1% percentile: 49 · as of 11 November 2026
- CWE
- CWE-1321
Could this be exploited in your environment?
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