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CVE-2021-23393

Estado: ModificadaMedia (5.4)—

This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_url function, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as \\\evil.com/path. This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using 'autocorrect_location_header=False.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Flask Unchained Project — Flask Unchained

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-23393",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 5.8,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:P/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 4.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": true
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "report@snyk.io",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.4,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 2.8
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.4,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "report@snyk.io",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "Flask-Unchained",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "0.9.0",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-06-11T00:15:09.273",
  "references": [
    {
      "url": "https://github.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "report@snyk.io"
    },
    {
      "url": "https://snyk.io/vuln/SNYK-PYTHON-FLASKUNCHAINED-1293189",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "report@snyk.io"
    },
    {
      "url": "https://github.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://snyk.io/vuln/SNYK-PYTHON-FLASKUNCHAINED-1293189",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-601"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_url function, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as \\\\\\evil.com/path. This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using 'autocorrect_location_header=False."
    },
    {
      "lang": "es",
      "value": "Esto afecta al paquete Flask-Unchained versiones anteriores a 0.9.0. Cuando se usa la función _validate_redirect_url, es posible omitir la comprobación de la URL y redireccionar a un usuario a una URL arbitraria proporcionando múltiples barras invertidas, como por ejemplo \\\\\\evil.com/path. Esta vulnerabilidad sólo es explotable si un servidor WSGI alternativo a Werkzeug es usado, o se modifica el comportamiento por defecto de Werkzeug usando \"autocorrect_location_header=False"
    }
  ],
  "lastModified": "2026-06-17T03:38:40.823",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:flask_unchained_project:flask_unchained:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "4491B634-FD96-4E0C-9584-EB97EBC710F1",
              "versionEndExcluding": "0.9.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "report@snyk.io"
}