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Vulnerabilities

Vulnerability · CVE-2025-66456

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication.

Published Dec 9, 2025 · catalog updated Oct 14, 2026 · Elysia is a Typescript

Check if you run it

No confirmed exploitation is on record for CVE-2025-66456. EPSS is 0.56%. Act only if a listed version of Elysia is a Typescript is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Elysia is a Typescript).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.56%
Remediation
Advisory link
Affected products
cpe elysiajs/elysia

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 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 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 from body.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe elysiajs/elysiaversion unspecified

How to fix CVE-2025-66456

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-66456. EPSS is 0.56%. Act only if a listed version of Elysia is a Typescript is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). EPSS 0.56%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 9, 2025 · NIST NVD

    Detected

    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 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 to be mer

  2. Oct 14, 2026 · NIST NVD

    Updated

    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 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 to be mer

Sources

  • CVE.orgVulnerability recordCVE-2025-66456

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-66456

    30-day exploitation probability 0.6%

    first.org
  • NIST NVDVulnerability recordCVE-2025-66456

    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 after merging results of two standard schema validations with t

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.