How severe is CVE-2025-66457?

CVE-2025-66457 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-66457 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66457?

CVE-2025-66457 affects Elysiajs Elysia. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-66457?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-66457 have an EU (EUVD) identifier?

Yes. CVE-2025-66457 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-202179.

When was CVE-2025-66457 published?

CVE-2025-66457 was published on 2025-12-09 and last updated on 2026-06-17.

CVE-2025-66457

CVE-2025-66457 is a high-severity vulnerability in Elysiajs Elysia with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-94.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v4: 7.5
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-202179
Weakness: CWE-94
Affected product: Elysiajs Elysia
Published: 2025-12-09
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2025-66457?: 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.
How severe is CVE-2025-66457?: CVE-2025-66457 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-66457 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66457?: CVE-2025-66457 affects Elysiajs Elysia. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-66457?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-66457 have an EU (EUVD) identifier?: Yes. CVE-2025-66457 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-202179.
When was CVE-2025-66457 published?: CVE-2025-66457 was published on 2025-12-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:elysiajs:elysia:*:*:*:*:*:node.js:*:*

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