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CVE-2026-46274

Estado: AnalizadaAlta (7.8)—

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

io-wq: check that the predecessor is hashed in io_wq_remove_pending()

io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled work was the tail of its hash bucket. When doing this, it checks whether the preceding entry in acct->work_list has the same hash value, but never checks that the predecessor is hashed at all. io_get_work_hash() is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash bits are never set for non-hashed work, so it returns 0. Thus, when a hashed bucket-0 work is cancelled while a non-hashed work is its list predecessor, the check spuriously passes and a pointer to the non-hashed io_kiocb is stored in wq->hash_tail[0].

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Because non-hashed work is dequeued via the fast path in io_get_next_work(), which never touches hash_tail[], the stale pointer is never cleared. Therefore, after the non-hashed io_kiocb completes and is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The io_wq is per-task (tctx->io_wq) and survives ring open/close, so the dangling pointer persists for the lifetime of the task; the next hashed bucket-0 enqueue dereferences it in io_wq_insert_work() and wq_list_add_after() writes through freed memory.

Add the missing io_wq_is_hashed() check so a non-hashed predecessor never inherits a hash_tail[] slot.

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) sin interacción de usuario en kernel Linux que permite escalada de privilegios mediante corrupción de memoria (use-after-free, CWE-416), permitiendo ejecución de código arbitrario como root.

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

Execution PreventionThreat Intelligence ProgramRestrict Web-Based ContentPrivileged Account ManagementLimit Software InstallationFilter Network Traffic

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\nio-wq: check that the predecessor is hashed in io_wq_remove_pending()\n\nio_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled\nwork was the tail of its hash bucket. When doing this, it checks whether\nthe preceding entry in acct->work_list has the same hash value, but\nnever checks that the predecessor is hashed at all. io_get_work_hash()\nis simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash\nbits are never set for non-hashed work, so it returns 0. Thus, when a\nhashed bucket-0 work is cancelled while a non-hashed work is its list\npredecessor, the check spuriously passes and a pointer to the non-hashed\nio_kiocb is stored in wq->hash_tail[0].\n\nBecause non-hashed work is dequeued via the fast path in\nio_get_next_work(), which never touches hash_tail[], the stale pointer\nis never cleared. Therefore, after the non-hashed io_kiocb completes and\nis freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The\nio_wq is per-task (tctx->io_wq) and survives ring open/close, so the\ndangling pointer persists for the lifetime of the task; the next hashed\nbucket-0 enqueue dereferences it in io_wq_insert_work() and\nwq_list_add_after() writes through freed memory.\n\nAdd the missing io_wq_is_hashed() check so a non-hashed predecessor\nnever inherits a hash_tail[] slot."
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      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nio-wq: verificar que el predecesor esté hasheado en io_wq_remove_pending()\n\nio_wq_remove_pending() necesita corregir wq->hash_tail[] si el trabajo cancelado era la cola de su cubo hash. Al hacer esto, verifica si la entrada precedente en acct->work_list tiene el mismo valor hash, pero nunca verifica que el predecesor esté hasheado en absoluto. io_get_work_hash() es simplemente atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, y los bits hash nunca se establecen para trabajos no hasheados, por lo que devuelve 0. Así, cuando un trabajo hasheado del cubo 0 es cancelado mientras que un trabajo no hasheado es su predecesor en la lista, la verificación pasa de forma espuria y un puntero al io_kiocb no hasheado se almacena en wq->hash_tail[0].\n\nDebido a que el trabajo no hasheado se desencola a través de la ruta rápida en io_get_next_work(), que nunca toca hash_tail[], el puntero obsoleto nunca se borra. Por lo tanto, después de que el io_kiocb no hasheado se completa y se libera de nuevo a req_cachep, wq->hash_tail[0] es un puntero colgante. El io_wq es por tarea (tctx->io_wq) y sobrevive a la apertura/cierre del anillo, por lo que el puntero colgante persiste durante la vida útil de la tarea; la siguiente encolación hasheada del cubo 0 lo desreferencia en io_wq_insert_work() y wq_list_add_after() escribe a través de memoria liberada.\n\nAñadir la verificación io_wq_is_hashed() faltante para que un predecesor no hasheado nunca herede una ranura hash_tail[]."
    }
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  "lastModified": "2026-07-23T07:10:00.113",
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