CVE-2026-6270

Summary

@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 Software

Weaknesses

• CWE-436: CWE-436: Interpretation Conflict

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: no
  • Technical Impact: total

References

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

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