CVE-2021-21330

Status: ModifiedMedium (6.1)—

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. In aiohttp before version 3.7.4 there is an open redirect vulnerability. A maliciously crafted link to an aiohttp-based web-server could redirect the browser to a different website. It is caused by a bug in the `aiohttp.web_middlewares.normalize_path_middleware` middleware. This security problem has been fixed in 3.7.4. Upgrade your dependency using pip as follows "pip install aiohttp >= 3.7.4". If upgrading is not an option for you, a workaround can be to avoid using `aiohttp.web_middlewares.normalize_path_middleware` in your applications.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Base score: 6.1

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 1.91%
Percentile among all scored CVEs: 79
Score date: 10/7/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (3)

Aiohttp — Aiohttp Debian — Debian Linux Fedoraproject — Fedora

CWEs

CWE-601
CWE-601

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2021-21330",
  "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": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 3.1,
          "attackVector": "NETWORK",
          "baseSeverity": "LOW",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 1.6
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 6.1,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.7,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "aio-libs",
          "product": "aiohttp",
          "versions": [
            {
              "status": "affected",
              "version": "< 3.7.4"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-02-26T03:15:12.840",
  "references": [
    {
      "url": "https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96b",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L/",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5/",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://pypi.org/project/aiohttp/",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-19",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4864",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96b",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://pypi.org/project/aiohttp/",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-19",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4864",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-601"
        }
      ]
    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-601"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. In aiohttp before version 3.7.4 there is an open redirect vulnerability. A maliciously crafted link to an aiohttp-based web-server could redirect the browser to a different website. It is caused by a bug in the `aiohttp.web_middlewares.normalize_path_middleware` middleware. This security problem has been fixed in 3.7.4. Upgrade your dependency using pip as follows \"pip install aiohttp >= 3.7.4\". If upgrading is not an option for you, a workaround can be to avoid using `aiohttp.web_middlewares.normalize_path_middleware` in your applications."
    },
    {
      "lang": "es",
      "value": "aiohttp es un framework cliente/servidor HTTP asincrónico para asyncio y Python.&#xa0;En aiohttp versiones anteriores a 3.7.4, se presenta una vulnerabilidad de redireccionamiento abierto.&#xa0;Un enlace diseñado malicioso en un servidor web basado en aiohttp podría redireccionar el navegador a un sitio web diferente.&#xa0;Es causado por un error en el middleware \"aiohttp.web_middlewares.normalize_path_middleware\".&#xa0;Este problema de seguridad ha sido corregido en versión 3.7.4.&#xa0;Actualice su dependencia usando pip de la siguiente manera \"pip install aiohttp versiones posteriores o incluyendo a 3.7.4\".&#xa0;Si la actualización no es una opción para usted, una solución alternativa puede ser evitar el uso de \"aiohttp.web_middlewares.normalize_path_middleware\" en sus aplicaciones"
    }
  ],
  "lastModified": "2026-06-17T03:35:18.640",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "85039D6B-2E1A-4679-8345-BD3804144EAC",
              "versionEndExcluding": "3.7.4"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "07B237A9-69A3-4A9C-9DA0-4E06BD37AE73"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E460AA51-FCDA-46B9-AE97-E6676AA5E194"
            },
            {
              "criteria": "cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "A930E247-0B43-43CB-98FF-6CE7B8189835"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security-advisories@github.com"
}