CVE-2026-6270

@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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://cna.openjsf.org/security-advisories.html	Vendor Advisory
https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c	Exploit Mitigation Vendor Advisory
https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:fastify:fastify\/middie:*:*:*:*:*:node.js:*:*

History

No history.

Information

Published : 2026-04-16 14:16

Updated : 2026-06-17 11:00

NVD link : CVE-2026-6270

Mitre link : CVE-2026-6270

CVE.ORG link : CVE-2026-6270

JSON object : View

Products Affected

fastify

fastify\/middie

CWE

CWE-436

Interpretation Conflict

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