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CVE-2021-33026

Estado: ModificadaCrítica (9.8)—💥 PoC

The Flask-Caching extension through 1.10.1 for Flask relies on Pickle for serialization, which may lead to remote code execution or local privilege escalation. If an attacker gains access to cache storage (e.g., filesystem, Memcached, Redis, etc.), they can construct a crafted payload, poison the cache, and execute Python code. NOTE: a third party indicates that exploitation is extremely unlikely unless the machine is already compromised; in other cases, the attacker would be unable to write their payload to the cache and generate the required collision

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)

Flask-caching Project — Flask-caching

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-33026",
  "cveTags": [
    {
      "tags": [
        "disputed"
      ],
      "sourceIdentifier": "cve@mitre.org"
    }
  ],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-33026",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2024-07-19T18:22:56.685627Z"
        }
      }
    ],
    "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": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
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          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
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  "affected": [
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      "affectedData": [
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      "affectedData": [
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          "product": "flask-caching",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "custom",
              "lessThanOrEqual": "1.10.1"
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  ],
  "published": "2021-05-13T23:15:07.367",
  "references": [
    {
      "url": "https://github.com/pallets-eco/flask-caching/pull/209#issuecomment-1136397937",
      "tags": [
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        "Patch",
        "Third Party Advisory"
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      "source": "cve@mitre.org"
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      "tags": [
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      "description": [
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      "description": [
        {
          "lang": "en",
          "value": "CWE-502"
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    {
      "lang": "en",
      "value": "The Flask-Caching extension through 1.10.1 for Flask relies on Pickle for serialization, which may lead to remote code execution or local privilege escalation. If an attacker gains access to cache storage (e.g., filesystem, Memcached, Redis, etc.), they can construct a crafted payload, poison the cache, and execute Python code. NOTE: a third party indicates that exploitation is extremely unlikely unless the machine is already compromised; in other cases, the attacker would be unable to write their payload to the cache and generate the required collision"
    },
    {
      "lang": "es",
      "value": "** EN DISPUTA ** La extensión Flask-Caching hasta la versión 1.10.1 para Flask se basa en Pickle para la serialización, lo que puede llevar a la ejecución remota de código o a la escalada local de privilegios. Si un atacante obtiene acceso al almacenamiento de la caché (por ejemplo, el sistema de archivos, Memcached, Redis, etc.), puede construir una carga útil manipulada, envenenar la caché y ejecutar código Python. NOTA: un tercero indica que la explotación es extremadamente improbable a menos que la máquina ya esté comprometida; en otros casos, el atacante no podría escribir su carga útil en la caché y generar la colisión necesaria"
    }
  ],
  "lastModified": "2026-06-17T03:54:02.267",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:flask-caching_project:flask-caching:*:*:*:*:*:flask:*:*",
              "vulnerable": true,
              "matchCriteriaId": "04389DFA-32B3-4F65-BBDB-6321BA631F81",
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          "operator": "OR"
        }
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  "sourceIdentifier": "cve@mitre.org"
}