Interpretation Conflict Affecting @fastify/middie package, versions <9.2.0
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- published1 Mar 2026
- disclosed27 Feb 2026
- creditUnknown
Introduced: 27 Feb 2026
NewCVE-2026-2880 (opens in a new tab)Common Vulnerabilities and Exposures (CVE) are common identifiers for publicly known security vulnerabilities
Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade @fastify/middie to version 9.2.0 or higher.
Overview
@fastify/middie is a Middleware engine for Fastify
Affected versions of this package are vulnerable to Interpretation Conflict via the middleware matching engine when router options like ignoreDuplicateSlashes, useSemicolonDelimiter, or other trailing-slash normalization are enabled. An attacker can bypass path-scoped authorization middleware and reach protected handlers by sending crafted normalized variants such as //secret, /secret;foo=bar, or /secret/.