CVE-2026-112362 (GCVE-0-2026-112362)

Vulnerability from cvelistv5 – Published: 2026-10-27 11:27 – Updated: 2026-10-27 11:27
VLAI
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.
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 CNA under the redhat root
CNA scorecard C 65/100 over 121 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
@fastify/express @fastify/express Affected: 4.0.5 , < 4.0.9 (semver)
Unaffected: 4.0.9 (semver)
guessed Create a notification for this product.
Credits
agent-killjoy mcollina UlisesGascon
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/@fastify/express",
          "product": "@fastify/express",
          "vendor": "@fastify/express",
          "versions": [
            {
              "lessThan": "4.0.9",
              "status": "affected",
              "version": "4.0.5",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "4.0.9",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "agent-killjoy"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "mcollina"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "UlisesGascon"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "@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\u0027s scheme, so Fastify\u0027s 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."
            }
          ],
          "value": "@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\u0027s scheme, so Fastify\u0027s 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_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",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-436",
              "description": "CWE-436: Interpretation Conflict",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-27T11:27:59.364Z",
        "orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "shortName": "openjs"
      },
      "references": [
        {
          "url": "https://github.com/fastify/fastify-express/security/advisories/GHSA-6h42-57hq-9746"
        },
        {
          "url": "https://cna.openjsf.org/security-advisories.html"
        }
      ],
      "title": "@fastify/express vulnerable to path-scoped middleware bypass via absolute-form request targets",
      "x_generator": {
        "engine": "cve-kit 1.0.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
    "assignerShortName": "openjs",
    "cveId": "CVE-2026-112362",
    "datePublished": "2026-10-27T11:27:59.364Z",
    "dateReserved": "2026-10-19T14:59:03.468Z",
    "dateUpdated": "2026-10-27T11:27:59.364Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "packageURL": "pkg:npm/@fastify/express",
                "product": "@fastify/express",
                "vendor": "@fastify/express",
                "versions": [
                  {
                    "lessThan": "4.0.9",
                    "status": "affected",
                    "version": "4.0.5",
                    "versionType": "semver"
                  },
                  {
                    "status": "unaffected",
                    "version": "4.0.9",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "@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\u0027s scheme, so Fastify\u0027s 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."
          }
        ],
        "id": "CVE-2026-112362",
        "lastModified": "2026-10-27T15:03:41.023",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 9.1,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.2,
              "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-27T12:17:04.970",
        "references": [
          {
            "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
            "url": "https://cna.openjsf.org/security-advisories.html"
          },
          {
            "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
            "url": "https://github.com/fastify/fastify-express/security/advisories/GHSA-6h42-57hq-9746"
          }
        ],
        "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "vulnStatus": "Awaiting Analysis",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-436"
              }
            ],
            "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
            "type": "Secondary"
          }
        ]
      }
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.