@fastify/express vulnerable to path-scoped middleware bypass via absolute-form request targets

{
  "id": "af5eb731910f8a8ab5f2d75c151c94bc0cbc499d0007260cefbdb4341aceb742",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-112362",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "@fastify/express vulnerable to path-scoped middleware bypass via absolute-form request targets",
    "summary": "@fastify/express is a Fastify plugin that runs Express middleware inside Fastify. In versions 4.0.5 through 4.0.8, when Fastify runs with the non-default ignoreDuplicateSlashes option enabled, the plugin matches path-scoped Express middleware against a URL whose duplicate-slash normalization has also collapsed the separator after an absolute-form request target's scheme, so Fastify's router resolves the request to the scoped path and runs the handler while the Express layer no longer sees that path. As a result, a request using an absolute-form target can reach a handler on a scoped route such as an admin path while the middleware for authentication, authorization, or rate limiting is skipped. An unauthenticated attacker needs only the non-default ignoreDuplicateSlashes option to be enabled. The issue is fixed in @fastify/express 4.0.9, and users should upgrade to 4.0.9 or later. As a workaround, enforce authentication in a Fastify hook such as preHandler that runs after the router resolves the request, or leave ignoreDuplicateSlashes at its default.",
    "evidence": "cve:CVE-2026-112362",
    "products": [
      {
        "name": {
          "value": "@fastify/express",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-112362",
      "aliases": [
        "CVE-2026-112362"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV3_1": {
            "version": "3.1",
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "affected": [
        {
          "vendor": "@fastify/express",
          "product": "@fastify/express",
          "versions": [
            {
              "status": "affected",
              "version": "4.0.5",
              "lessThan": "4.0.9",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "4.0.9",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:npm/@fastify/express",
          "defaultStatus": "unaffected"
        }
      ],
      "modified": "2026-10-27T11:27:59.364Z",
      "provider": "cve",
      "references": [
        "https://github.com/fastify/fastify-express/security/advisories/GHSA-6h42-57hq-9746",
        "https://cna.openjsf.org/security-advisories.html"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
          "shortName": "openjs",
          "dateUpdated": "2026-10-27T11:27:59.364Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-112362",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 391940,
  "published_at": "2026-10-27T11:27:59.364+00:00"
}