CVE-2026-2880
Received Received - Intake
Authorization Bypass in @fastify/middie via Path-Scoped Middleware

Publication date: 2026-02-27

Last updated on: 2026-03-19

Assigner: openjs

Description
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.
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Meta Information
Published
2026-02-27
Last Modified
2026-03-19
Generated
2026-06-16
AI Q&A
2026-02-27
EPSS Evaluated
2026-06-14
NVD
CVE-2026-2880
EUVD
EUVD-2026-9049
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
openjsf @fastify/middie to 9.2.0 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
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Executive Summary

This vulnerability exists in @fastify/middie versions prior to 9.2.0 and allows an attacker to bypass authentication and authorization checks when using path-scoped middleware.

Specifically, when Fastify router normalization options like ignoreDuplicateSlashes, useSemicolonDelimiter, or trailing-slash behavior are enabled, crafted request paths can circumvent middleware protections while still reaching protected handlers.

Impact Analysis

This vulnerability can lead to unauthorized access to protected routes or resources within an application using the affected @fastify/middie versions.

Attackers can exploit crafted request paths to bypass authentication and authorization middleware, potentially exposing sensitive data or functionality that should be restricted.

Compliance Impact

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Detection Guidance

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Mitigation Strategies

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