CVE-2026-6270

critical · 9.1

@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.

9.1

CVSS

0.5%

EPSS (exploit prob.)

42nd

EPSS percentile

2026-04-16

Published

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Weaknesses

CWE-436

Affected products

Vendor	Product	Affected versions
fastify	fastify/middie	< 9.3.2

Check a specific version with /api/v1/cve/match.

References

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

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-6270