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Description

@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.

PUBLISHED Reserved 2026-04-14 | Published 2026-04-16 | Updated 2026-04-16 | Assigner openjs




CRITICAL: 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Problem types

CWE-436: Interpretation Conflict

Product status

Default status
unaffected

Any version before 9.3.2
affected

9.3.2 (semver)
unaffected

Credits

FredKSchott reporter

climba03003 remediation developer

UlisesGascon remediation developer

References

github.com/...xpress/security/advisories/GHSA-hrwm-hgmj-7p9c

github.com/...middie/security/advisories/GHSA-72c6-fx6q-fr5w

cna.openjsf.org/security-advisories.html

cve.org (CVE-2026-6270)

nvd.nist.gov (CVE-2026-6270)

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