CVE-2021-29492

{
  "id": "CVE-2021-29492",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 7.5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "HIGH",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.1,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 2.2
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 8.3,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 3.7,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "envoyproxy",
          "product": "envoy",
          "versions": [
            {
              "status": "affected",
              "version": "<= 1.18.2"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-05-28T21:15:08.670",
  "references": [
    {
      "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-4987-27fx-x6cf",
      "tags": [
        "Mitigation",
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-4987-27fx-x6cf",
      "tags": [
        "Mitigation",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-22"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Envoy is a cloud-native edge/middle/service proxy. Envoy does not decode escaped slash sequences `%2F` and `%5C` in HTTP URL paths in versions 1.18.2 and before. A remote attacker may craft a path with escaped slashes, e.g. `/something%2F..%2Fadmin`, to bypass access control, e.g. a block on `/admin`. A backend server could then decode slash sequences and normalize path and provide an attacker access beyond the scope provided for by the access control policy. ### Impact Escalation of Privileges when using RBAC or JWT filters with enforcement based on URL path. Users with back end servers that interpret `%2F` and `/` and `%5C` and `\\` interchangeably are impacted. ### Attack Vector URL paths containing escaped slash characters delivered by untrusted client. Patches in versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. As a workaround, if back end servers treat `%2F` and `/` and `%5C` and `\\` interchangeably and a URL path based access control is configured, one may reconfigure the back end server to not treat `%2F` and `/` and `%5C` and `\\` interchangeably."
    },
    {
      "lang": "es",
      "value": "Envoy es un proxy de borde/medio/servicio nativo de la nube. Envoy no descifra las secuencias de barras diagonales escapadas `%2F` y `%5C` en las rutas URL HTTP en las versiones 1.18.2 y anteriores. Un atacante remoto puede crear una ruta con barras escapadas, por ejemplo `algo%2F..%2Fadmin`, para saltarse el control de acceso, por ejemplo, un bloqueo en `/admin`. Un servidor backend podría entonces decodificar las secuencias de barras y normalizar la ruta y proporcionar a un atacante acceso más allá del alcance previsto por la política de control de acceso. ### Impacto Escalada de Privilegios cuando se utilizan filtros RBAC o JWT con aplicación basada en la ruta de la URL. Los usuarios con servidores de back-end que interpretan `%2F` y `/` y `%5C` y `\\` indistintamente están impactados. ### Vector de ataque Rutas de URL que contienen caracteres de barra diagonal escapados entregados por un cliente que no es de confianza. Los parches de las versiones 1.18.3, 1.17.3, 1.16.4 y 1.15.5 contienen una nueva opción de normalización de rutas para descodificar los caracteres de barra diagonal escapados. Como solución, si los servidores finales tratan `%2F` y `/` y `%5C` y `\\` indistintamente y se configura un control de acceso basado en la ruta de la URL, se puede reconfigurar el servidor final para que no trate `%2F` y `/` y `%5C` y `\\` indistintamente"
    }
  ],
  "lastModified": "2026-06-17T03:47:45.130",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "EE9E311E-85FF-42AA-B0A3-C138D436932D",
              "versionEndExcluding": "1.15.5"
            },
            {
              "criteria": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "D36D66BB-9C95-4E59-AA78-6824ACCB89D7",
              "versionEndExcluding": "1.16.4",
              "versionStartIncluding": "1.16.0"
            },
            {
              "criteria": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "D502D5F9-38A7-46B1-890D-2A177B76AEBB",
              "versionEndExcluding": "1.17.3",
              "versionStartIncluding": "1.17.0"
            },
            {
              "criteria": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "BA3D8EC7-7D60-41C5-9770-3521DB6F7650",
              "versionEndExcluding": "1.18.3",
              "versionStartIncluding": "1.18.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security-advisories@github.com"
}