Vulnerability Report

CVE-2026-2880

Title: Authentication/Authorization Bypass in @fastify/middie

Input Validation Error

Proof Of Concept

No public PoC currently indexed for CVE-2026-2880.

CWE Category CWE-20

Published Date Feb 27, 2026

Modified Date May 14, 2026

Exploit Status Not Found

Score 8.2 CVSS v4.0

Exploit Probability (EPSS)

0.09%

Vulnerability Summary

CVE-2026-2880: 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.

Impacted Vendors

openjsf 1

fastify 1

Reference Links

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

CVSS v4.0

Source Entity ce714d77-add3-4f53-aff5-83d477b104bb

Severity HIGH

8.2

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

N/A

RAW VECTOR

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1

Source Entity [email protected]

Severity CRITICAL

9.1