CVE-2026-31865: Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-ser

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-31865 is a medium-severity flaw (CVSS 6.5) affecting elysia. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-1321
Published	2026-03-18
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: elysiajs

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-18 04:17 UTCPublished CVE record published
2026-06-17 10:34 UTCUpdated Record last modified

elysiajs elysia UPGRADE

Affected: < 1.4.27

Fixed in: 1.4.27

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls elysia

2. UPGRADE to 1.4.27

npm install elysia@">=1.4.27"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-31865?

elysia: upgrade to 1.4.27. Exact commands for each OS are on this page.

Is CVE-2026-31865 being exploited?

CVE-2026-31865 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-31865 affect?

CVE-2026-31865 affects elysia. Severity is medium (CVSS 6.5). 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 issu

How urgent is CVE-2026-31865?

Priority 32/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2025-66456 CRITICAL 9.8 UPGRADE Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-serv
CVE-2025-66457 HIGH 8.8 UPGRADE Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-serv
CVE-2026-30837 HIGH 7.5 UPGRADE Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-serv

References

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