CVE-2018-20852

Estado: ModificadaMedia (5.3)—

http.cookiejar.DefaultPolicy.domain_return_ok in Lib/http/cookiejar.py in Python before 3.7.3 does not correctly validate the domain: it can be tricked into sending existing cookies to the wrong server. An attacker may abuse this flaw by using a server with a hostname that has another valid hostname as a suffix (e.g., pythonicexample.com to steal cookies for example.com). When a program uses http.cookiejar.DefaultPolicy and tries to do an HTTP connection to an attacker-controlled server, existing cookies can be leaked to the attacker. This affects 2.x through 2.7.16, 3.x before 3.4.10, 3.5.x before 3.5.7, 3.6.x before 3.6.9, and 3.7.x before 3.7.3.

CVSS

Versión: 3.0
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Puntuación base: 5.3

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 3.88%
Percentil entre todas las CVEs puntuadas: 90
Fecha de la puntuación: 5/10/2026

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)

Python — Python

CWE

CWE-20

Referencias

JSON original (NVD)

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{
  "id": "CVE-2018-20852",
  "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
      }
    ],
    "cvssMetricV30": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2019-07-13T21:15:10.377",
  "references": [
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      "url": "http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00071.html",
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      "source": "cve@mitre.org"
    },
    {
      "url": "https://python-security.readthedocs.io/vuln/cookie-domain-check.html",
      "tags": [
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    {
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://python-security.readthedocs.io/vuln/cookie-domain-check.html",
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.oracle.com/security-alerts/cpuapr2020.html",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "http.cookiejar.DefaultPolicy.domain_return_ok in Lib/http/cookiejar.py in Python before 3.7.3 does not correctly validate the domain: it can be tricked into sending existing cookies to the wrong server. An attacker may abuse this flaw by using a server with a hostname that has another valid hostname as a suffix (e.g., pythonicexample.com to steal cookies for example.com). When a program uses http.cookiejar.DefaultPolicy and tries to do an HTTP connection to an attacker-controlled server, existing cookies can be leaked to the attacker. This affects 2.x through 2.7.16, 3.x before 3.4.10, 3.5.x before 3.5.7, 3.6.x before 3.6.9, and 3.7.x before 3.7.3."
    },
    {
      "lang": "es",
      "value": "http.cookiejar.DefaultPolicy.domain_return_ok en Lib / http / cookiejar.py en Python en versiones anteriores a la 3.7.3 no valida correctamente el dominio: se puede engañar para que envíe las cookies existentes al servidor incorrecto. Un atacante puede abusar de este fallo al usar un servidor con un nombre de host que tiene otro nombre de host válido como sufijo (por ejemplo, pythonicexample.com para robar cookies para example.com). Cuando un programa utiliza http.cookiejar.DefaultPolicy e intenta hacer una conexión HTTP a un servidor controlado por un atacante, las cookies existentes pueden ser filtradas al atacante. Esto afecta a la versión 2.x hasta la versión 2.7.16, versión 3.x en versiones anteriores a la 3.4.10, versión 3.5.x en versiones anteriores a la 3.5.7, versión 3.6.x en versiones anteriores a la 3.6.9 y versión 3.7.x en versiones anteriores a la 3.7.3."
    }
  ],
  "lastModified": "2026-06-17T01:53:35.820",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:python:python:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "573B27AF-F9CA-4DA8-89B2-6AD6D61CDFDE",
              "versionEndIncluding": "2.7.16",
              "versionStartIncluding": "2.0"
            },
            {
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              "matchCriteriaId": "C1E55AC4-366D-497C-A541-A7BA86084846",
              "versionEndExcluding": "3.4.10",
              "versionStartIncluding": "3.0.0"
            },
            {
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              "vulnerable": true,
              "matchCriteriaId": "BA03C7E0-BBBD-48B7-8B55-D21114F7AE78",
              "versionEndExcluding": "3.5.7",
              "versionStartIncluding": "3.5.0"
            },
            {
              "criteria": "cpe:2.3:a:python:python:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "2C052B2D-757B-4342-8BE9-510A08599779",
              "versionEndExcluding": "3.6.9",
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            },
            {
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              "matchCriteriaId": "4C910F83-E507-4572-93B0-740BFBA89B7A",
              "versionEndExcluding": "3.7.3",
              "versionStartIncluding": "3.7.0"
            }
          ],
          "operator": "OR"
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  "sourceIdentifier": "cve@mitre.org"
}