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CVE-2026-23235

Estado: AnalizadaAlta (7.1)—

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

f2fs: fix out-of-bounds access in sysfs attribute read/write

Some f2fs sysfs attributes suffer from out-of-bounds memory access and incorrect handling of integer values whose size is not 4 bytes.

For example: vm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out vm:~# cat /sys/fs/f2fs/vde/carve_out 65537 vm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold vm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold 1

carve_out maps to {struct f2fs_sb_info}->carve_out, which is a 8-bit integer. However, the sysfs interface allows setting it to a value larger than 255, resulting in an out-of-range update.

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atgc_age_threshold maps to {struct atgc_management}->age_threshold, which is a 64-bit integer, but its sysfs interface cannot correctly set values larger than UINT_MAX.

The root causes are: 1. __sbi_store() treats all default values as unsigned int, which prevents updating integers larger than 4 bytes and causes out-of-bounds writes for integers smaller than 4 bytes.

2. f2fs_sbi_show() also assumes all default values are unsigned int, leading to out-of-bounds reads and incorrect access to integers larger than 4 bytes.

This patch introduces {struct f2fs_attr}->size to record the actual size of the integer associated with each sysfs attribute. With this information, sysfs read and write operations can correctly access and update values according to their real data size, avoiding memory corruption and truncation.

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).

🎯 Técnicas ATT&CK

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

Vulnerabilidad local (AV:L/PR:L) en kernel Linux sin interacción: escalada de privilegios mediante corrupción de memoria en atributos sysfs. Acceso a datos del kernel (C:H) e integridad afectada (I:H).

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

Threat Intelligence ProgramRestrict File and Directory PermissionsRemote Data StorageExecution PreventionEncrypt Sensitive InformationApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix out-of-bounds access in sysfs attribute read/write\n\nSome f2fs sysfs attributes suffer from out-of-bounds memory access and\nincorrect handling of integer values whose size is not 4 bytes.\n\nFor example:\nvm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out\nvm:~# cat /sys/fs/f2fs/vde/carve_out\n65537\nvm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold\nvm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold\n1\n\ncarve_out maps to {struct f2fs_sb_info}->carve_out, which is a 8-bit\ninteger. However, the sysfs interface allows setting it to a value\nlarger than 255, resulting in an out-of-range update.\n\natgc_age_threshold maps to {struct atgc_management}->age_threshold,\nwhich is a 64-bit integer, but its sysfs interface cannot correctly set\nvalues larger than UINT_MAX.\n\nThe root causes are:\n1. __sbi_store() treats all default values as unsigned int, which\nprevents updating integers larger than 4 bytes and causes out-of-bounds\nwrites for integers smaller than 4 bytes.\n\n2. f2fs_sbi_show() also assumes all default values are unsigned int,\nleading to out-of-bounds reads and incorrect access to integers larger\nthan 4 bytes.\n\nThis patch introduces {struct f2fs_attr}->size to record the actual size\nof the integer associated with each sysfs attribute. With this\ninformation, sysfs read and write operations can correctly access and\nupdate values according to their real data size, avoiding memory\ncorruption and truncation."
    },
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      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nf2fs: corrige el acceso fuera de límites en la lectura/escritura de atributos sysfs\n\nAlgunos atributos sysfs de f2fs sufren de acceso a memoria fuera de límites y manejo incorrecto de valores enteros cuyo tamaño no es de 4 bytes.\n\nPor ejemplo:\nvm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out\nvm:~# cat /sys/fs/f2fs/vde/carve_out\n65537\nvm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold\nvm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold\n1\n\ncarve_out se mapea a {struct f2fs_sb_info}->carve_out, que es un entero de 8 bits. Sin embargo, la interfaz sysfs permite establecerlo a un valor mayor que 255, lo que resulta en una actualización fuera de rango.\n\natgc_age_threshold se mapea a {struct atgc_management}->age_threshold, que es un entero de 64 bits, pero su interfaz sysfs no puede establecer correctamente valores mayores que UINT_MAX.\n\nLas causas raíz son:\n1. __sbi_store() trata todos los valores predeterminados como unsigned int, lo que impide actualizar enteros mayores de 4 bytes y causa escrituras fuera de límites para enteros menores de 4 bytes.\n\n2. f2fs_sbi_show() también asume que todos los valores predeterminados son unsigned int, lo que lleva a lecturas fuera de límites y acceso incorrecto a enteros mayores de 4 bytes.\n\nEste parche introduce {struct f2fs_attr}->size para registrar el tamaño real del entero asociado con cada atributo sysfs. Con esta información, las operaciones de lectura y escritura de sysfs pueden acceder y actualizar valores correctamente según su tamaño de datos real, evitando la corrupción de memoria y la truncación."
    }
  ],
  "lastModified": "2026-06-17T10:21:09.440",
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