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CVE-2026-2880

@fastify/middie has an improper path normalization vulnerability

Published: Feb 27, 2026Updated: May 14, 2026 Sources: CVE List NVD GHSACWE-20
NVD MITRE
9.1CVSSCRITICAL
EPSS Score
0.4%
Top 69.4%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:N
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\/middiefastify
Library
OSS Libraries / web-framework
@fastify/middienpmOSS Libraries
@fastify/middie@fastify/middie
Library
OSS Libraries / web-framework
fastifyoss-projectOSS Librariesaka fastify/middie, fastify-multipart
npmpackage-ecosystemOSS Libraries
@fastify/middieoss-projectUSOSS Librariesaka @fastify/middie, fastify-middie

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available
Workaround Available

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

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 →

Timeline

Published
Feb 27, 2026
Last Updated
May 14, 2026

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