Medium 6.5Published Mar 17, 2026

CVE-2026-31865Elysia Cookie Value Prototype Pollution

Updated under an hour ago (Oct 27, 2026, 11:40 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for elysiajs elysia

Exploited in the last 30 days

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.

CVSS: 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness (CWE): CWE-1321
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

elysiajs elysia elysiajs:elysia (from the name)	before 1.4.27	CNA record
elysiajs elysia elysiajs:elysia	before 1.4.27	NVD

References

References

https://github.com/elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp	x-refsource-confirm, mitigation, patch, vendor-advisory
https://github.com/elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab	x-refsource-misc, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.