CVE-2024-50217

Estado: ModificadaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()

Mounting btrfs from two images (which have the same one fsid and two different dev_uuids) in certain executing order may trigger an UAF for variable 'device->bdev_file' in __btrfs_free_extra_devids(). And following are the details:

Fix it by setting 'device->bdev_file' as 'NULL' after closing the btrfs_device in btrfs_close_one_device().

Detalles técnicos trazas, registros y código del informe original

1. Attach image_1 to loop0, attach image_2 to loop1, and scan btrfs
   devices by ioctl(BTRFS_IOC_SCAN_DEV):

             /  btrfs_device_1 → loop0
   fs_device
             \  btrfs_device_2 → loop1
2. mount /dev/loop0 /mnt
   btrfs_open_devices
    btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0)
    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
   btrfs_fill_super
    open_ctree
     fail: btrfs_close_devices // -ENOMEM
	    btrfs_close_bdev(btrfs_device_1)
             fput(btrfs_device_1->bdev_file)
	      // btrfs_device_1->bdev_file is freed
	    btrfs_close_bdev(btrfs_device_2)
             fput(btrfs_device_2->bdev_file)

3. mount /dev/loop1 /mnt
   btrfs_open_devices
    btrfs_get_bdev_and_sb(&bdev_file)
     // EIO, btrfs_device_1->bdev_file is not assigned,
     // which points to a freed memory area
    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
   btrfs_fill_super
    open_ctree
     btrfs_free_extra_devids
      if (btrfs_device_1->bdev_file)
       fput(btrfs_device_1->bdev_file) // UAF !

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.28%
Percentil entre todas las CVEs puntuadas: 18
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).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation75 %
Impacto principalT1059 Command and Scripting Interpreterexecution60 %
Impacto secundarioT1499.004 Application or System Exploitationimpact55 %

UAF en kernel de Linux (CWE-416) con acceso local (AV:L, PR:L) sin interacción. Requiere escalada de privilegios T1068. Impacto: ejecución de código arbitrario (T1059) o DoS (T1499.004) por corrupción de memoria.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Execution Prevention Threat Intelligence Program Restrict Web-Based Content Privileged Account Management Limit Software Installation Filter Network Traffic

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416
CWE-416

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()\n\nMounting btrfs from two images (which have the same one fsid and two\ndifferent dev_uuids) in certain executing order may trigger an UAF for\nvariable 'device->bdev_file' in __btrfs_free_extra_devids(). And\nfollowing are the details:\n\n1. Attach image_1 to loop0, attach image_2 to loop1, and scan btrfs\n   devices by ioctl(BTRFS_IOC_SCAN_DEV):\n\n             /  btrfs_device_1 → loop0\n   fs_device\n             \\  btrfs_device_2 → loop1\n2. mount /dev/loop0 /mnt\n   btrfs_open_devices\n    btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0)\n    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)\n   btrfs_fill_super\n    open_ctree\n     fail: btrfs_close_devices // -ENOMEM\n\t    btrfs_close_bdev(btrfs_device_1)\n             fput(btrfs_device_1->bdev_file)\n\t      // btrfs_device_1->bdev_file is freed\n\t    btrfs_close_bdev(btrfs_device_2)\n             fput(btrfs_device_2->bdev_file)\n\n3. mount /dev/loop1 /mnt\n   btrfs_open_devices\n    btrfs_get_bdev_and_sb(&bdev_file)\n     // EIO, btrfs_device_1->bdev_file is not assigned,\n     // which points to a freed memory area\n    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)\n   btrfs_fill_super\n    open_ctree\n     btrfs_free_extra_devids\n      if (btrfs_device_1->bdev_file)\n       fput(btrfs_device_1->bdev_file) // UAF !\n\nFix it by setting 'device->bdev_file' as 'NULL' after closing the\nbtrfs_device in btrfs_close_one_device()."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: se corrige el use-after-free del archivo del dispositivo de bloque en __btrfs_free_extra_devids(). Montar btrfs desde dos imágenes (que tienen el mismo fsid y dos dev_uuids diferentes) en cierto orden de ejecución puede activar un UAF para la variable 'device-&gt;bdev_file' en __btrfs_free_extra_devids(). Y a continuación se muestran los detalles: 1. Adjunte image_1 a loop0, adjunte image_2 a loop1 y escanee los dispositivos btrfs con ioctl(BTRFS_IOC_SCAN_DEV): / btrfs_device_1 ? loop0 fs_device \\ btrfs_device_2 ? loop1 2. monte /dev/loop0 /mnt btrfs_open_devices btrfs_device_1-&gt;bdev_file = btrfs_get_bdev_and_sb(loop0) btrfs_device_2-&gt;bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree fail: btrfs_close_devices // -ENOMEM btrfs_close_bdev(btrfs_device_1) fput(btrfs_device_1-&gt;bdev_file) // btrfs_device_1-&gt;bdev_file se libera btrfs_close_bdev(btrfs_device_2) fput(btrfs_device_2-&gt;bdev_file) 3. mount /dev/loop1 /mnt btrfs_open_devices btrfs_get_bdev_and_sb(&amp;bdev_file) // EIO, btrfs_device_1-&gt;bdev_file no está asignado, // lo que apunta a un área de memoria liberada btrfs_device_2-&gt;bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree btrfs_free_extra_devids if (btrfs_device_1-&gt;bdev_file) fput(btrfs_device_1-&gt;bdev_file) // UAF! Arréglelo configurando 'device-&gt;bdev_file' como 'NULL' después de cerrar btrfs_device en btrfs_close_one_device()."
    }
  ],
  "lastModified": "2026-08-04T11:21:33.953",
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