critical9.1
CVE-2026-6270
@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances.
Impact
@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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @fastify/middie | <= 9.3.1 | 9.3.2 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Fastify | Fastify\/Middie | before 9.3.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-72c6-fx6q-fr5w
- https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
- https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w
- https://nvd.nist.gov/vuln/detail/CVE-2026-6270
- https://cna.openjsf.org/security-advisories.html