CVE-2026-6270 — @fastify/middie vulnerable to middleware authentication bypass in child plugin scopes
@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 mi…
Published: 2026-04-16 · CVSS: 9.1 · CVSS 3.1
@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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7