Vulnerability-Lookup

CVE-2026-2880 (GCVE-0-2026-2880)

Vulnerability from cvelistv5 – Published: 2026-02-27 18:25 – Updated: 2026-02-27 18:56

Title

@fastify/middie has an improper path normalization vulnerability

Summary

A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.

Severity

8.2 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-02-27 18:55 UTC

CWE

CWE-20

Assigner

openjs redhat root Scorecard

References

1 reference

URL	Tags
https://github.com/fastify/middie/security/adviso…

Impacted products

1 product

Vendor	Product	Version	CPE status
@fastify/middie	@fastify/middie	Affected: 0.0.0 , < 9.2.0 (semver)	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-2880

Vulnerability from fkie_nvd - Published: 2026-02-27 19:16 - Updated: 2026-06-17 10:31

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://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	fastify	fastify\/middie	*

JSON

To clipboard

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          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-2880",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-02-27T18:55:36.300396Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-02-27T19:16:12.807",
  "references": [
    {
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "tags": [
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw"
    }
  ],
  "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ],
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "type": "Secondary"
    }
  ]
}

GHSA-8P85-9QPW-FWGW

Vulnerability from github – Published: 2026-02-28 02:47 – Updated: 2026-02-28 02:47

Summary

@fastify/middie has Improper Path Normalization when Using Path-Scoped Middleware

Details

Summary

A path normalization inconsistency in @fastify/middie can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).

When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.

Impact

An unauthenticated remote attacker can access endpoints intended to be protected by middleware-based auth/authorization controls by sending specially crafted URL paths (for example, //secret or /secret;foo=bar), depending on router option configuration.

This may lead to unauthorized access to protected functionality and data exposure.

Affected versions

Confirmed affected: @fastify/middie@9.1.0
All versions prior to the patch are affected.

Patched versions

Fixed in: 9.2.0

Details

The issue is caused by canonicalization drift between: 1. @fastify/middie path matching for app.use('/prefix', ...), and 2. Fastify/find-my-way route lookup normalization.

Because middleware and router did not always evaluate the same normalized path, auth middleware could be skipped while route resolution still succeeded.

Workarounds

Until patched version is deployed: - Avoid relying solely on path-scoped middie guards for auth/authorization. - Enforce auth at route-level handlers/hooks after router normalization. - Disable risky normalization combinations only if operationally feasible.

Resources

Fluid Attacks Disclosure Policy: https://fluidattacks.com/advisories/policy
Fluid Attacks advisory URL: https://fluidattacks.com/advisories/jimenez

Credits

Cristian Vargas (Fluid Attacks Research Team) — discovery and report.
Oscar Uribe (Fluid Attacks) — coordination and disclosure.

Severity

8.2 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@fastify/middie"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-2880"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-28T02:47:17Z",
    "nvd_published_at": "2026-02-27T19:16:12Z",
    "severity": "HIGH"
  },
  "details": "## Summary\nA path normalization inconsistency in `@fastify/middie` can result in authentication/authorization bypass when using path-scoped middleware (for example, `app.use(\u0027/secret\u0027, auth)`).\n\nWhen Fastify router normalization options are enabled (such as `ignoreDuplicateSlashes`, `useSemicolonDelimiter`, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.\n\n## Impact\nAn unauthenticated remote attacker can access endpoints intended to be protected by middleware-based auth/authorization controls by sending specially crafted URL paths (for example, `//secret` or `/secret;foo=bar`), depending on router option configuration.\n\nThis may lead to unauthorized access to protected functionality and data exposure.\n\n## Affected versions\n- Confirmed affected: `@fastify/middie@9.1.0`\n- All versions prior to the patch are affected.\n\n## Patched versions\n- Fixed in: *9.2.0*\n\n## Details\nThe issue is caused by canonicalization drift between:\n1. `@fastify/middie` path matching for `app.use(\u0027/prefix\u0027, ...)`, and\n2. Fastify/find-my-way route lookup normalization.\n\nBecause middleware and router did not always evaluate the same normalized path, auth middleware could be skipped while route resolution still succeeded.\n\n## Workarounds\nUntil patched version is deployed:\n- Avoid relying solely on path-scoped middie guards for auth/authorization.\n- Enforce auth at route-level handlers/hooks after router normalization.\n- Disable risky normalization combinations only if operationally feasible.\n\n## Resources\n- Fluid Attacks Disclosure Policy: https://fluidattacks.com/advisories/policy\n- Fluid Attacks advisory URL: https://fluidattacks.com/advisories/jimenez\n\n## Credits\n- **Cristian Vargas** (Fluid Attacks Research Team) \u2014 discovery and report.\n- **Oscar Uribe** (Fluid Attacks) \u2014 coordination and disclosure.",
  "id": "GHSA-8p85-9qpw-fwgw",
  "modified": "2026-02-28T02:47:17Z",
  "published": "2026-02-28T02:47:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-2880"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/middie/commit/140e0dd0359d890fec7e6ea1dcc5134d6bd554d4"
    },
    {
      "type": "WEB",
      "url": "https://fluidattacks.com/advisories/jimenez"
    },
    {
      "type": "WEB",
      "url": "https://fluidattacks.com/advisories/policy"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fastify/middie"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/middie/releases/tag/v9.2.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "@fastify/middie has Improper Path Normalization when Using Path-Scoped Middleware"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

CVE-2026-2880 (GCVE-0-2026-2880)

FKIE_CVE-2026-2880

GHSA-8P85-9QPW-FWGW

Summary

Impact

Affected versions

Patched versions

Details

Workarounds

Resources

Credits

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