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@fastify/middie vulnerable to path-scoped middleware bypass via scope prefix mismatch

Type: advisorySource: Official CVE List1 source record

@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.

Announced Group revision 1
Original source ↗

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
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