How severe is CVE-2026-31865?

CVE-2026-31865 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-31865 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31865?

CVE-2026-31865 affects Elysiajs Elysia. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31865?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-31865 have an EU (EUVD) identifier?

Yes. CVE-2026-31865 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12749.

When was CVE-2026-31865 published?

CVE-2026-31865 was published on 2026-03-18 and last updated on 2026-06-17.

CVE-2026-31865

CVE-2026-31865 is a medium-severity vulnerability in Elysiajs Elysia with a CVSS 3.x base score of 6.5. 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-1321.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-12749
Weakness: CWE-1321
Affected product: Elysiajs Elysia
Published: 2026-03-18
Last modified: 2026-06-17

Description

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible.

Frequently asked questions

What is CVE-2026-31865?: Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible.
How severe is CVE-2026-31865?: CVE-2026-31865 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-31865 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31865?: CVE-2026-31865 affects Elysiajs Elysia. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31865?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-31865 have an EU (EUVD) identifier?: Yes. CVE-2026-31865 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12749.
When was CVE-2026-31865 published?: CVE-2026-31865 was published on 2026-03-18 and last updated on 2026-06-17.

References

Affected products (1)

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

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