CVE-2024-49884
Estado: ModificadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix slab-use-after-free in ext4_split_extent_at()
We hit the following use-after-free:
The flow of issue triggering is as follows:
So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path.
In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates.
Detalles técnicos trazas, registros y código del informe original
==================================================================
BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0
Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40
CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724
Call Trace:
<TASK>
kasan_report+0x93/0xc0
ext4_split_extent_at+0xba8/0xcc0
ext4_split_extent.isra.0+0x18f/0x500
ext4_split_convert_extents+0x275/0x750
ext4_ext_handle_unwritten_extents+0x73e/0x1580
ext4_ext_map_blocks+0xe20/0x2dc0
ext4_map_blocks+0x724/0x1700
ext4_do_writepages+0x12d6/0x2a70
[...]
Allocated by task 40:
__kmalloc_noprof+0x1ac/0x480
ext4_find_extent+0xf3b/0x1e70
ext4_ext_map_blocks+0x188/0x2dc0
ext4_map_blocks+0x724/0x1700
ext4_do_writepages+0x12d6/0x2a70
[...]
Freed by task 40:
kfree+0xf1/0x2b0
ext4_find_extent+0xa71/0x1e70
ext4_ext_insert_extent+0xa22/0x3260
ext4_split_extent_at+0x3ef/0xcc0
ext4_split_extent.isra.0+0x18f/0x500
ext4_split_convert_extents+0x275/0x750
ext4_ext_handle_unwritten_extents+0x73e/0x1580
ext4_ext_map_blocks+0xe20/0x2dc0
ext4_map_blocks+0x724/0x1700
ext4_do_writepages+0x12d6/0x2a70
[...]
==================================================================
ext4_split_extent_at
path = *ppath
ext4_ext_insert_extent(ppath)
ext4_ext_create_new_leaf(ppath)
ext4_find_extent(orig_path)
path = *orig_path
read_extent_tree_block
// return -ENOMEM or -EIO
ext4_free_ext_path(path)
kfree(path)
*orig_path = NULL
a. If err is -ENOMEM:
ext4_ext_dirty(path + path->p_depth)
// path use-after-free !!!
b. If err is -EIO and we have EXT_DEBUG defined:
ext4_ext_show_leaf(path)
eh = path[depth].p_hdr
// path also use-after-free !!!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: 0.27%
- Percentil entre todas las CVEs puntuadas: 17
- Fecha de la puntuación: 6/10/2026
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.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation75 % - Impacto principal
T1059Command and Scripting Interpreterexecution60 % - Impacto secundario
T1499.004Application or System Exploitationimpact55 %
CWE-416 (use-after-free) en kernel local (AV:L, PR:L) permite escalada de privilegios. Potencial ejecución de código o DoS en el contexto del kernel.
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
Tecnologías afectadas (2)
CWE
- CWE-416
Referencias
- https://git.kernel.org/stable/c/393a46f60ea4f249dc9d496d4eb2d542f5e11ade
- https://git.kernel.org/stable/c/448100a29395b0c8b4c42967155849fe0fbe808f
- https://git.kernel.org/stable/c/5d949ea75bb529ea6342e83465938a3b0ac51238
- https://git.kernel.org/stable/c/8fe117790b37c84c651e2bad9efc0e7fda73c0e3
- https://git.kernel.org/stable/c/915ac3630488af0ca194dc63b86d99802b4f6e18
- https://git.kernel.org/stable/c/a5401d4c3e2a3d25643c567d26e6de327774a2c9
- https://git.kernel.org/stable/c/c26ab35702f8cd0cdc78f96aa5856bfb77be798f
- https://git.kernel.org/stable/c/cafcc1bd62934547c76abf46c6d0d54f135006fe
- https://git.kernel.org/stable/c/e52f933598b781d291b9297e39c463536da0e185
- https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
- https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
JSON original (NVD)
Mostrar
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix slab-use-after-free in ext4_split_extent_at()\n\nWe hit the following use-after-free:\n\n==================================================================\nBUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0\nRead of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40\nCPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724\nCall Trace:\n <TASK>\n kasan_report+0x93/0xc0\n ext4_split_extent_at+0xba8/0xcc0\n ext4_split_extent.isra.0+0x18f/0x500\n ext4_split_convert_extents+0x275/0x750\n ext4_ext_handle_unwritten_extents+0x73e/0x1580\n ext4_ext_map_blocks+0xe20/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n\nAllocated by task 40:\n __kmalloc_noprof+0x1ac/0x480\n ext4_find_extent+0xf3b/0x1e70\n ext4_ext_map_blocks+0x188/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n\nFreed by task 40:\n kfree+0xf1/0x2b0\n ext4_find_extent+0xa71/0x1e70\n ext4_ext_insert_extent+0xa22/0x3260\n ext4_split_extent_at+0x3ef/0xcc0\n ext4_split_extent.isra.0+0x18f/0x500\n ext4_split_convert_extents+0x275/0x750\n ext4_ext_handle_unwritten_extents+0x73e/0x1580\n ext4_ext_map_blocks+0xe20/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n==================================================================\n\nThe flow of issue triggering is as follows:\n\next4_split_extent_at\n path = *ppath\n ext4_ext_insert_extent(ppath)\n ext4_ext_create_new_leaf(ppath)\n ext4_find_extent(orig_path)\n path = *orig_path\n read_extent_tree_block\n // return -ENOMEM or -EIO\n ext4_free_ext_path(path)\n kfree(path)\n *orig_path = NULL\n a. If err is -ENOMEM:\n ext4_ext_dirty(path + path->p_depth)\n // path use-after-free !!!\n b. If err is -EIO and we have EXT_DEBUG defined:\n ext4_ext_show_leaf(path)\n eh = path[depth].p_hdr\n // path also use-after-free !!!\n\nSo when trying to zeroout or fix the extent length, call ext4_find_extent()\nto update the path.\n\nIn addition we use *ppath directly as an ext4_ext_show_leaf() input to\navoid possible use-after-free when EXT_DEBUG is defined, and to avoid\nunnecessary path updates."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ext4: corrección de slab-use-after-free en ext4_split_extent_at() Nos topamos con el siguiente use after free: ====================================================================== ERROR: KASAN: slab-use-after-free en ext4_split_extent_at+0xba8/0xcc0 Lectura de tamaño 2 en la dirección ffff88810548ed08 por la tarea kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 No contaminado 6.9.0-dirty #724 Seguimiento de llamadas: kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Asignado por la tarea 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Liberado por la tarea 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ==================================================================== El flujo de activación del problema es el siguiente: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // devuelve -ENOMEM o -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. Si err es -ENOMEM: ext4_ext_dirty(path + path->p_depth) // ¡¡¡path use after free!!! b. Si err es -EIO y tenemos EXT_DEBUG definido: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // ¡¡¡La ruta también es use after free!!! Por lo tanto, cuando intente poner a cero o corregir la longitud de la extensión, llame a ext4_find_extent() para actualizar la ruta. Además, usamos *ppath directamente como una entrada de ext4_ext_show_leaf() para evitar un posible use after free cuando se define EXT_DEBUG y para evitar actualizaciones de ruta innecesarias."
}
],
"lastModified": "2026-08-04T11:20:56.083",
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