# CVE-2026-6270

## Summary

- **CVE ID:** CVE-2026-6270
- **Severity:** CRITICAL
- **CVSS Score:** 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)
- **CWE:** CWE-436
- **Published:** Apr 16, 2026
- **Last Modified:** Apr 16, 2026

## Description

@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the parent middleware. This allows unauthenticated requests to reach routes defined in child plugin scopes, bypassing authentication and authorization checks. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds.

## Affected Products

- @fastify/middie — @fastify/middie (0)
- @fastify/middie — @fastify/middie (9.3.2)

## References

- [CNA](https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c)
- [CNA](https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w)
- [CNA](https://cna.openjsf.org/security-advisories.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.50%
- **EPSS Percentile:** 41.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._