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CVE-2021-3864

Estado: ModificadaAlta (7)—💥 PoC

Se ha encontrado un fallo en la forma en que es manejada la configuración del flag volcable cuando determinados binarios SUID ejecutan sus descendientes. El prerrequisito es un binario SUID que establece el UID real igual al UID efectivo, y el GID real igual al GID efectivo. El descendiente tendrá entonces un valor descargable establecido en 1. Como resultado, si el proceso descendiente es bloqueado y core_pattern es establecido en un valor relativo, su volcado de núcleo es almacenado en el directorio actual con permisos uid:gid. Un usuario local no privilegiado con el binario SUID de root podría usar este fallo para colocar los volcados de núcleo en directorios propiedad de root, lo que podría resultar en una escalada de privilegios.

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 (3)

Debian — Debian LinuxLinux — Linux KernelRedhat — Enterprise Linux

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-3864",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1
      }
    ]
  },
  "affected": [
    {
      "source": "secalert@redhat.com",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "kernel",
          "versions": [
            {
              "status": "affected",
              "version": "Not Known"
            }
          ]
        }
      ]
    }
  ],
  "published": "2022-08-26T16:15:09.680",
  "references": [
    {
      "url": "https://access.redhat.com/security/cve/CVE-2021-3864",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2015046",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/",
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/",
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/",
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://security-tracker.debian.org/tracker/CVE-2021-3864",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://www.openwall.com/lists/oss-security/2021/10/20/2",
      "tags": [
        "Exploit",
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://access.redhat.com/security/cve/CVE-2021-3864",
      "tags": [
        "Third Party Advisory"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2015046",
      "tags": [
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        "Patch",
        "Third Party Advisory"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security-tracker.debian.org/tracker/CVE-2021-3864",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.openwall.com/lists/oss-security/2021/10/20/2",
      "tags": [
        "Exploit",
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "secalert@redhat.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-284"
        }
      ]
    },
    {
      "type": "Secondary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants. The prerequisite is a SUID binary that sets real UID equal to effective UID, and real GID equal to effective GID. The descendant will then have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, its core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root SUID binary could use this flaw to place core dumps into root-owned directories, potentially resulting in escalation of privileges."
    },
    {
      "lang": "es",
      "value": "Se ha encontrado un fallo en la forma en que es manejada la configuración del flag volcable cuando determinados binarios SUID ejecutan sus descendientes. El prerrequisito es un binario SUID que establece el UID real igual al UID efectivo, y el GID real igual al GID efectivo. El descendiente tendrá entonces un valor descargable establecido en 1. Como resultado, si el proceso descendiente es bloqueado y core_pattern es establecido en un valor relativo, su volcado de núcleo es almacenado en el directorio actual con permisos uid:gid. Un usuario local no privilegiado con el binario SUID de root podría usar este fallo para colocar los volcados de núcleo en directorios propiedad de root, lo que podría resultar en una escalada de privilegios."
    }
  ],
  "lastModified": "2026-06-17T04:05:55.150",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "703AF700-7A70-47E2-BC3A-7FD03B3CA9C1"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
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            },
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "FA6FEEC2-9F11-4643-8827-749718254FED"
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    {
      "nodes": [
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  "sourceIdentifier": "secalert@redhat.com"
}