PT-2026-33320 · @Fastify/Middie · @Fastify/Middie

Climba03003 + 2 · Published 2026-04-16 · Updated 2026-04-16 · CVE-2026-6270

Mitre

CVSS v3.1

9.1

Critical

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

@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.

Fix

Weakness Enumeration

CWE-436

Related Identifiers

CVE-2026-6270

Affected Products

@Fastify/Middie

References · 4

• https://nvd.nist.gov/vuln/detail/CVE-2026-6270 · Security Note
• https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c · Note
• https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w · Note
• https://cna.openjsf.org/security-advisories.html · Note