Vulnerability-Lookup

CVE-2026-6270 (GCVE-0-2026-6270)

Vulnerability from cvelistv5 – Published: 2026-04-16 13:44 – Updated: 2026-04-16 14:24

Title

@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes

Summary

@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the parent middleware. This allows unauthenticated requests to reach routes defined in child plugin scopes, bypassing authentication and authorization checks. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds.

Severity ?

9.1 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CWE

CWE-436 - Interpretation Conflict

Assigner

openjs

References

URL

Tags

	https://github.com/fastify/fastify-express/securi…
	https://github.com/fastify/middie/security/adviso…
	https://cna.openjsf.org/security-advisories.html

Impacted products

	Vendor	Product	Version
	@fastify/middie	@fastify/middie	Affected: 0 , < 9.3.2 (semver) Unaffected: 9.3.2 (semver)

Credits

FredKSchott climba03003 UlisesGascon

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-6270

Vulnerability from fkie_nvd - Published: 2026-04-16 14:16 - Updated: 2026-04-17 15:17

Severity ?

9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	ce714d77-add3-4f53-aff5-83d477b104bb	https://cna.openjsf.org/security-advisories.html
	ce714d77-add3-4f53-aff5-83d477b104bb	https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
	ce714d77-add3-4f53-aff5-83d477b104bb	https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the parent middleware. This allows unauthenticated requests to reach routes defined in child plugin scopes, bypassing authentication and authorization checks. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds."
    }
  ],
  "id": "CVE-2026-6270",
  "lastModified": "2026-04-17T15:17:00.957",
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    },
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}

GHSA-72C6-FX6Q-FR5W

Vulnerability from github – Published: 2026-04-16 22:29 – Updated: 2026-04-16 22:29

Summary

@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes

Details

Impact

@fastify/middie v9.3.1 and earlier incorrectly re-prefixes middleware paths when propagating them to child plugin scopes. When a child plugin is registered with a prefix that overlaps with a parent-scoped middleware path, the middleware path is modified during inheritance and silently fails to match incoming requests.

This results in complete bypass of middleware security controls for all routes defined within affected child plugin scopes, including nested (grandchild) scopes. Authentication, authorization, rate limiting, and any other middleware-based security mechanisms are skipped. No special request crafting or configuration is required.

This is the same vulnerability class as GHSA-hrwm-hgmj-7p9c (CVE-2026-33807) in @fastify/express.

Patches

Upgrade to @fastify/middie v9.3.2 or later.

Workarounds

None. Upgrade to the patched version.

Severity ?

9.1 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 9.3.1"
      },
      "package": {
        "ecosystem": "npm",
        "name": "@fastify/middie"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-6270"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-436"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T22:29:04Z",
    "nvd_published_at": "2026-04-16T14:16:19Z",
    "severity": "CRITICAL"
  },
  "details": "### Impact\n\n`@fastify/middie` v9.3.1 and earlier incorrectly re-prefixes middleware paths when propagating them to child plugin scopes. When a child plugin is registered with a prefix that overlaps with a parent-scoped middleware path, the middleware path is modified during inheritance and silently fails to match incoming requests.\n\nThis results in complete bypass of middleware security controls for all routes defined within affected child plugin scopes, including nested (grandchild) scopes. Authentication, authorization, rate limiting, and any other middleware-based security mechanisms are skipped. No special request crafting or configuration is required.\n\nThis is the same vulnerability class as [GHSA-hrwm-hgmj-7p9c](https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c) (CVE-2026-33807) in `@fastify/express`.\n\n### Patches\n\nUpgrade to `@fastify/middie` v9.3.2 or later.\n\n### Workarounds\n\nNone. Upgrade to the patched version.",
  "id": "GHSA-72c6-fx6q-fr5w",
  "modified": "2026-04-16T22:29:04Z",
  "published": "2026-04-16T22:29:04Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6270"
    },
    {
      "type": "WEB",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fastify/middie"
    }
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  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-6270 (GCVE-0-2026-6270)

FKIE_CVE-2026-6270

GHSA-72C6-FX6Q-FR5W

Impact

Patches

Workarounds

Tags

Sightings

Nomenclature