@fastify/middie vulnerable to path-scoped middleware bypass via scope prefix mismatch
@fastify/middie is the Express-style middleware engine for Fastify. In versions from 9.0.0 through 9.3.5, the use() function joined a path-scoped middleware's mount path to the plugin scope prefix in a way that could diverge from the path Fastify's router serves, most often when the scope prefix ended in a slash, and also for array mount paths and for mount paths written without a leading slash. When the two paths disagreed, the middleware was silently skipped while the route handler still ran, so path-scoped middleware such as authentication, authorization, or rate limiting could be bypassed by a single unauthenticated request. The issue is fixed in @fastify/middie 9.3.6, and users should upgrade to 9.3.6 or later. As a workaround, enforce authorization in a Fastify hook such as preHandler that runs after the router has resolved the request.
CVE-2026-112712
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-112712
@fastify/middie
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "@fastify/middie",
"product": "@fastify/middie",
"versions": [
{
"status": "affected",
"version": "9.0.0",
"lessThan": "9.3.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "9.3.6",
"versionType": "semver"
}
],
"packageURL": "pkg:npm/@fastify/middie",
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-112712
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #42643 · Revision 1
- Added to Heist Feed
- Publisher date