CVE-2026-53198
Estado: AnalizadaAlta (8.8)—
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL
A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_requests via setup_async_work(), with cancel_fn = smb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock.
When the request is cancelled, the worker frees the file_lock with locks_free_lock() and takes the cancelled early-exit, which "goto out"s and never reaches release_async_work() -- the only site that unlinks the work from conn->async_requests and clears cancel_fn/cancel_argv.
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The work therefore stays matchable on async_requests with a live cancel_fn pointing at the freed file_lock, until connection teardown finally runs release_async_work().
smb2_cancel() fires cancel_fn unconditionally with no state guard, so a second SMB2_CANCEL for the same AsyncId, arriving in that window, re-runs smb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free:
Reproduced on mainline with KASAN by an authenticated SMB client.
Skip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback cannot be fired a second time.
Detalles técnicos trazas, registros y código del informe original
BUG: KASAN: slab-use-after-free in __locks_delete_block
__locks_delete_block
locks_delete_block
ksmbd_vfs_posix_lock_unblock
smb2_remove_blocked_lock
smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn
handle_ksmbd_work
Allocated by ...: locks_alloc_lock <- smb2_lock
Freed by ...: locks_free_lock <- smb2_lock (cancelled branch)
... cache file_lock_cache of size 192CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 8.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.43%
- Percentil entre todas las CVEs puntuadas: 36
- 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
T1210Exploitation of Remote Serviceslateral movement85 % - Impacto principal
T1068Exploitation for Privilege Escalationprivilege escalation80 %
Vulnerabilidad de use-after-free en ksmbd (SMB2) accesible por usuario autenticado (PR:L) vía red; permite escalada de privilegios tras corromper memoria 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 (1)
CWE
- CWE-416
Referencias
- https://git.kernel.org/stable/c/0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd
- https://git.kernel.org/stable/c/14d2eee0193ac3cd1bf3d014373449f0b8d35d6d
- https://git.kernel.org/stable/c/2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694
- https://git.kernel.org/stable/c/89ae9df09d2c1fb4a4eb495c113a7ce1dca34147
- https://git.kernel.org/stable/c/b7063c7426ea5a4d15e01b60538718765392f49d
- https://git.kernel.org/stable/c/f580d27e8928828693df44ba2db0fffdbe11dfea
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL\n\nA deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on\nconn->async_requests via setup_async_work(), with cancel_fn =\nsmb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock.\n\nWhen the request is cancelled, the worker frees the file_lock with\nlocks_free_lock() and takes the cancelled early-exit, which \"goto out\"s and never\nreaches release_async_work() -- the only site that unlinks the work from\nconn->async_requests and clears cancel_fn/cancel_argv. The work therefore stays\nmatchable on async_requests with a live cancel_fn pointing at the freed file_lock,\nuntil connection teardown finally runs release_async_work().\n\nsmb2_cancel() fires cancel_fn unconditionally with no state guard, so a second\nSMB2_CANCEL for the same AsyncId, arriving in that window, re-runs\nsmb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free:\n\n BUG: KASAN: slab-use-after-free in __locks_delete_block\n __locks_delete_block\n locks_delete_block\n ksmbd_vfs_posix_lock_unblock\n smb2_remove_blocked_lock\n smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn\n handle_ksmbd_work\n Allocated by ...: locks_alloc_lock <- smb2_lock\n Freed by ...: locks_free_lock <- smb2_lock (cancelled branch)\n ... cache file_lock_cache of size 192\n\nReproduced on mainline with KASAN by an authenticated SMB client.\n\nSkip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback\ncannot be fired a second time."
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