CVE-2026-33804

· HIGHAnalyzed

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CVSS v3.1

7.4

EPSS

0.28%

Published

Apr 16, 2026

Modified

May 14, 2026

Public PoC / Exploit

All weaponized →

No public PoC or exploit code indexed for this CVE.

Links to public security research (Exploit-DB, Nuclei, Trickest, GitHub) for defensive use only.

Description

@fastify/middie versions 9.3.1 and earlier are vulnerable to middleware bypass when the deprecated Fastify ignoreDuplicateSlashes option is enabled. The middleware path matching logic does not account for duplicate slash normalization performed by Fastify's router, allowing requests with duplicate slashes to bypass middleware authentication and authorization checks. This only affects applications using the deprecated ignoreDuplicateSlashes option. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds other than disabling the ignoreDuplicateSlashes option.

CVSS Vector

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

Weaknesses (CWE)

CWE-436

Affected Products (1)

fastify · fastify\/middie (up to 9.3.2)vulnerable

References (2)

https://cna.openjsf.org/security-advisories.html

Vendor Advisory

https://github.com/fastify/middie/security/advisories/GHSA-v9ww-2j6r-98q6

MitigationVendor Advisory

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