CVE-2026-2880

@fastify/middie has an improper path normalization vulnerability

Published: Feb 27, 2026Updated: May 14, 2026 Sources: CVE List NVD GHSACWE-20

9.1CRITICAL

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:HConfidentiality

High

I:HIntegrity

High

A:NAvailability

None

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Weaknesses

CWE-20

Affected Products

fastify

oss-projectaka fastify-multipart, fastify/middie

fastify\/middieLibrary

OSS Libraries / web-framework

package-ecosystem

oss-project·USaka fastify-middie

@fastify/middieLibrary

OSS Libraries / web-framework

Exploitability

Official Patch Available

Workaround Available

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Initial Access

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References

https://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw

github.com

https://nvd.nist.gov/vuln/detail/CVE-2026-2880

nvd.nist.gov

https://github.com/fastify/middie/commit/140e0dd0359d890fec7e6ea1dcc5134d6bd554d4

github.com

and 4 more references View all →

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