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CVE-2021-43557

Estado: ModificadaAlta (7.5)—💥 PoC

The uri-block plugin in Apache APISIX before 2.10.2 uses $request_uri without verification. The $request_uri is the full original request URI without normalization. This makes it possible to construct a URI to bypass the block list on some occasions. For instance, when the block list contains "^/internal/", a URI like `//internal/` can be used to bypass it. Some other plugins also have the same issue. And it may affect the developer's custom plugin.

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).

💥 Exploits públicos

Hay código de explotación o plantillas de detección públicos. No es lo mismo que explotación activa confirmada (KEV), pero aumenta el riesgo: parchee con prioridad.

⚠️ Las pruebas de concepto de GitHub no están verificadas: algunas son falsas o contienen malware. No las ejecute nunca fuera de un laboratorio aislado.

Tecnologías afectadas (1)

Apache — Apisix

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-43557",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security@apache.org",
      "affectedData": [
        {
          "vendor": "Apache Software Foundation",
          "product": "Apache APISIX",
          "versions": [
            {
              "status": "affected",
              "version": "1.5",
              "lessThan": "Apache APISIX 1.5*",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-11-22T09:15:07.627",
  "references": [
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/22/1",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "security@apache.org"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/22/2",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "security@apache.org"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/23/1",
      "tags": [
        "Exploit",
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "security@apache.org"
    },
    {
      "url": "https://lists.apache.org/thread/18jyd458ptocr31rnkjs71w4h366mv7h",
      "tags": [
        "Exploit",
        "Mailing List",
        "Vendor Advisory"
      ],
      "source": "security@apache.org"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/22/1",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/22/2",
      "tags": [
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        "Third Party Advisory"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2021/11/23/1",
      "tags": [
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        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.apache.org/thread/18jyd458ptocr31rnkjs71w4h366mv7h",
      "tags": [
        "Exploit",
        "Mailing List",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-77"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The uri-block plugin in Apache APISIX before 2.10.2 uses $request_uri without verification. The $request_uri is the full original request URI without normalization. This makes it possible to construct a URI to bypass the block list on some occasions. For instance, when the block list contains \"^/internal/\", a URI like `//internal/` can be used to bypass it. Some other plugins also have the same issue. And it may affect the developer's custom plugin."
    },
    {
      "lang": "es",
      "value": "El plugin uri-block en Apache APISIX versiones anteriores a 2.10.2, usa $request_uri sin verificación. La $request_uri es la URI original completa de la petición sin normalizar. Esto hace posible construir un URI para evitar la lista de bloqueo en algunas ocasiones. Por ejemplo, cuando la lista de bloqueo contiene \"^/internal/\", puede usarse una URI como \"//internal/\" para omitirla. Algunos otros plugins también presentan el mismo problema. Y puede afectar al plugin personalizado del desarrollador"
    }
  ],
  "lastModified": "2026-06-17T04:11:07.910",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:apache:apisix:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E6E300E2-7036-4813-B7A7-48F922753C76",
              "versionEndExcluding": "2.10.2"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security@apache.org"
}