CVE-2025-21658
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
btrfs: avoid NULL pointer dereference if no valid extent tree
[BUG] Syzbot reported a crash with the following call trace:
[CAUSE] The reproducer is using a corrupted image where extent tree root is corrupted, thus forcing to use "rescue=all,ro" mount option to mount the image.
Then it triggered a scrub, but since scrub relies on extent tree to find where the data/metadata extents are, scrub_find_fill_first_stripe() relies on an non-empty extent root.
But unfortunately scrub_find_fill_first_stripe() doesn't really expect an NULL pointer for extent root, it use extent_root to grab fs_info and triggered a NULL pointer dereference.
Leer descripción completaMostrar menos
[FIX] Add an extra check for a valid extent root at the beginning of scrub_find_fill_first_stripe().
The new error path is introduced by 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots"), but that's pretty old, and later commit b979547513ff ("btrfs: scrub: introduce helper to find and fill sector info for a scrub_stripe") changed how we do scrub.
So for kernels older than 6.6, the fix will need manual backport.
Detalles técnicos trazas, registros y código del informe original
BTRFS info (device loop0): scrub: started on devid 1 BUG: kernel NULL pointer dereference, address: 0000000000000208 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G O 6.13.0-rc4-custom+ #206 Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs] Call Trace: <TASK> scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs] scrub_simple_mirror+0x175/0x260 [btrfs] scrub_stripe+0x5d4/0x6c0 [btrfs] scrub_chunk+0xbb/0x170 [btrfs] scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs] btrfs_scrub_dev+0x240/0x600 [btrfs] btrfs_ioctl+0x1dc8/0x2fa0 [btrfs] ? do_sys_openat2+0xa5/0xf0 __x64_sys_ioctl+0x97/0xc0 do_syscall_64+0x4f/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK>
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- 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).
Tecnologías afectadas (1)
CWE
- CWE-476
- CWE-476
Referencias
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: avoid NULL pointer dereference if no valid extent tree\n\n[BUG]\nSyzbot reported a crash with the following call trace:\n\n BTRFS info (device loop0): scrub: started on devid 1\n BUG: kernel NULL pointer dereference, address: 0000000000000208\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0\n Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI\n CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G O 6.13.0-rc4-custom+ #206\n Tainted: [O]=OOT_MODULE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs]\n Call Trace:\n <TASK>\n scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs]\n scrub_simple_mirror+0x175/0x260 [btrfs]\n scrub_stripe+0x5d4/0x6c0 [btrfs]\n scrub_chunk+0xbb/0x170 [btrfs]\n scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs]\n btrfs_scrub_dev+0x240/0x600 [btrfs]\n btrfs_ioctl+0x1dc8/0x2fa0 [btrfs]\n ? do_sys_openat2+0xa5/0xf0\n __x64_sys_ioctl+0x97/0xc0\n do_syscall_64+0x4f/0x120\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n </TASK>\n\n[CAUSE]\nThe reproducer is using a corrupted image where extent tree root is\ncorrupted, thus forcing to use \"rescue=all,ro\" mount option to mount the\nimage.\n\nThen it triggered a scrub, but since scrub relies on extent tree to find\nwhere the data/metadata extents are, scrub_find_fill_first_stripe()\nrelies on an non-empty extent root.\n\nBut unfortunately scrub_find_fill_first_stripe() doesn't really expect\nan NULL pointer for extent root, it use extent_root to grab fs_info and\ntriggered a NULL pointer dereference.\n\n[FIX]\nAdd an extra check for a valid extent root at the beginning of\nscrub_find_fill_first_stripe().\n\nThe new error path is introduced by 42437a6386ff (\"btrfs: introduce\nmount option rescue=ignorebadroots\"), but that's pretty old, and later\ncommit b979547513ff (\"btrfs: scrub: introduce helper to find and fill\nsector info for a scrub_stripe\") changed how we do scrub.\n\nSo for kernels older than 6.6, the fix will need manual backport."
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: evitar la desreferencia de puntero NULL si no hay un árbol de extensión válido [ERROR] Syzbot informó de un fallo con el siguiente seguimiento de llamada: Información de BTRFS (bucle de dispositivo 0): scrub: iniciado en devid 1 ERROR: desreferencia de puntero NULL del kernel, dirección: 0000000000000208 #PF: acceso de lectura de supervisor en modo kernel #PF: error_code(0x0000) - página no presente PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: cargado Tainted: G O 6.13.0-rc4-custom+ #206 Tainted: [O]=OOT_MODULE Nombre de hardware: PC estándar QEMU (Q35 + ICH9, 2009), BIOS desconocido 02/02/2022 RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs] Seguimiento de llamadas: Scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs] Scrub_simple_mirror+0x175/0x260 [btrfs] Scrub_stripe+0x5d4/0x6c0 [btrfs] Scrub_chunk+0xbb/0x170 [btrfs] Scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs] btrfs_scrub_dev+0x240/0x600 [btrfs] btrfs_ioctl+0x1dc8/0x2fa0 [btrfs] ? do_sys_openat2+0xa5/0xf0 __x64_sys_ioctl+0x97/0xc0 do_syscall_64+0x4f/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e [CAUSA] El reproductor está usando una imagen dañada donde la raíz del árbol de extensión está dañada, lo que obliga a usar la opción de montaje \"rescue=all,ro\" para montar la imagen. Luego, activó una limpieza, pero como la limpieza depende del árbol de extensión para encontrar dónde están las extensiones de datos/metadatos, scrub_find_fill_first_stripe() depende de una raíz de extensión no vacía. Pero desafortunadamente scrub_find_fill_first_stripe() no espera realmente un puntero NULL para la raíz de la extensión, usa extended_root para obtener fs_info y activa una desreferencia de puntero NULL. [SOLUCIÓN] Agregue una verificación adicional para una raíz de extensión válida al comienzo de scrub_find_fill_first_stripe(). La nueva ruta de error es introducida por 42437a6386ff (\"btrfs: introduce mount option rescue=ignorebadroots\"), pero eso es bastante antiguo, y el commit posterior b979547513ff (\"btrfs: scrub: introduce helper to find and fill sector info for a scrub_stripe\") cambió la forma en que realizamos el scrub. Entonces, para los kernels anteriores a 6.6, la solución necesitará una adaptación manual. "
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"lastModified": "2026-06-17T08:43:57.093",
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