CVE-2026-64239
In the Linux kernel, the following vulnerability has been resolved:
mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()
DAMON sysfs maintains the DAMOS tried region directory objects via a linked list. When the user requests refresh of the directories, DAMON sysfs removes all the region directories first, and then generate updated regions directory on the empty space. The removal function (damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects. Deletion of the container region object from the linked list is done inside the kobj release callback function.
If somehow the callback invocation is delayed, the list will contain regions list that gonna be freed. If the updated region directories creation is started in this situation, the list can be corrupted and use-after-free can happen.
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Because the kobj objects are managed by only DAMON sysfs, the issue cannot happen in normal situation. But, such delays can be made on kernels that built with CONFIG_DEBUG_KOBJECT_RELEASE. On the kernel, the issue can indeed be reproduced like below.
Fix the issue by removing the region object from the list when decrementing the reference count.
Also update damos_sysfs_populate_region_dir() to add the region object to the list only after the kobject_init_and_add() is success, so that fail of kobject_init_and_add() is not leaving the deallocated object on the list.
The issue was discovered [1] by Sashiko.
Detalles técnicos trazas, registros y código del informe original
# damo start --damos_action stat
# cd /sys/kernel/mm/damon/admin/kdamonds/0/
# for i in {1..10}; do echo update_schemes_tried_regions > state; done
# dmesg | grep underflow
[ 89.296152] refcount_t: underflow; 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: 0.12%
- Percentil entre todas las CVEs puntuadas: 1
- 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.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1059Command and Scripting Interpreterexecution75 %
Vulnerabilidad local (AV:L, PR:L) de use-after-free (CWE-416) en kernel Linux que permite escalada de privilegios y ejecución de código arbitrario con permisos elevados mediante corrupción de memoria en gestión de objetos 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 (1)
CWE
- CWE-416
Referencias
- https://git.kernel.org/stable/c/0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7
- https://git.kernel.org/stable/c/2c33177023c92e76806c535ddbffaa3d3fc37777
- https://git.kernel.org/stable/c/441f92f7d386b85bad16de49db95a307cba048a2
- https://git.kernel.org/stable/c/a5fa42214de55e43d165144727ce9facb9fc6b08
- https://git.kernel.org/stable/c/c0e37017a452addec873865c94cf7a665663a9b2
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/sysfs-schemes: delete tried region in regions_rmdirs()\n\nDAMON sysfs maintains the DAMOS tried region directory objects via a\nlinked list. When the user requests refresh of the directories, DAMON\nsysfs removes all the region directories first, and then generate updated\nregions directory on the empty space. The removal function\n(damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects. \nDeletion of the container region object from the linked list is done\ninside the kobj release callback function.\n\nIf somehow the callback invocation is delayed, the list will contain\nregions list that gonna be freed. If the updated region directories\ncreation is started in this situation, the list can be corrupted and\nuse-after-free can happen.\n\nBecause the kobj objects are managed by only DAMON sysfs, the issue cannot\nhappen in normal situation. But, such delays can be made on kernels that\nbuilt with CONFIG_DEBUG_KOBJECT_RELEASE. On the kernel, the issue can\nindeed be reproduced like below.\n\n # damo start --damos_action stat\n # cd /sys/kernel/mm/damon/admin/kdamonds/0/\n # for i in {1..10}; do echo update_schemes_tried_regions > state; done\n # dmesg | grep underflow\n [ 89.296152] refcount_t: underflow; use-after-free.\n\nFix the issue by removing the region object from the list when\ndecrementing the reference count.\n\nAlso update damos_sysfs_populate_region_dir() to add the region object to\nthe list only after the kobject_init_and_add() is success, so that fail of\nkobject_init_and_add() is not leaving the deallocated object on the list.\n\nThe issue was discovered [1] by Sashiko."
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"lastModified": "2026-08-13T17:25:56.233",
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