CVE-2026-46275
Estado: AnalizadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_uart: fix UAFs and race conditions in close and init paths
Vulnerabilities leading to Use-After-Free (UAF) and Null Pointer Dereference (NPD) conditions were observed in the lifecycle management of hci_uart.
The primary issue arises because the workqueues (init_ready and write_work) are only flushed/cancelled if the HCI_UART_PROTO_READY flag is set during TTY close. If a hangup occurs before setup completes, hci_uart_tty_close() skips the teardown of these workqueues and proceeds to free the `hu` struct. When the scheduled work executes later, it blindly dereferences the freed `hu` struct.
Detalles técnicos trazas, registros y código del informe original
Furthermore, several data races and UAFs were identified in the teardown sequence: 1. Calling hci_uart_flush() from hci_uart_close() without effectively disabling write_work causes a race condition where both can concurrently double-free hu->tx_skb. This happens because protocol timers can concurrently invoke hci_uart_tx_wakeup() and requeue write_work. 2. Calling hci_free_dev(hdev) before hu->proto->close(hu) causes a UAF when vendor specific protocol close callbacks dereference hu->hdev. 3. In the initialization error paths, failing to take the proto_lock write lock before clearing PROTO_READY leads to races with active readers. Additionally, hci_uart_tty_receive() accesses hu->hdev outside the read lock, leading to UAFs if the initialization error path frees hdev concurrently. Fix these synchronization and lifecycle issues by: 1. Re-ordering hci_uart_tty_close() to clear HCI_UART_PROTO_READY first, followed immediately by a cancel_work_sync(&hu->write_work). Clearing the flag locks out concurrent protocol timers from successfully invoking hci_uart_tx_wakeup(), effectively rendering the cancellation permanent and preventing the tx_skb double-free. 2. Note: Clearing PROTO_READY early causes hci_uart_close() to skip hu->proto->flush(). This is perfectly safe in the tty_close path because hu->proto->close() executes shortly after, which intrinsically purges all protocol SKB queues and tears down the state. 3. Relocating hu->proto->close(hu) strictly prior to hci_free_dev(hdev) across all close and error paths to prevent vendor-level UAFs. 4. Moving the hdev->stat.byte_rx increment in hci_uart_tty_receive() inside the proto_lock read-side critical section to safely synchronize with device unregistration. 5. Adding cancel_work_sync(&hu->write_work) to hci_uart_close() to safely flush the workqueue before hci_uart_flush() is invoked via the HCI core. 6. Utilizing cancel_work_sync() instead of disable_work_sync() across all paths to prevent permanently breaking user-space retry capabilities.
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: 0.13%
- Percentil entre todas las CVEs puntuadas: 2
- 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 secundario
T1499.004Application or System Exploitationimpact75 %
Acceso local sin interacción (AV:L, PR:L, UI:N) con impacto máximo. Las race conditions y UAF permiten escalada de privilegios o DoS. CWE-362 es race condition.
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-362
Referencias
- https://git.kernel.org/stable/c/192cb0f1ca706d9a1bc36ae0ad5f666d1e4fd894
- https://git.kernel.org/stable/c/7338031946bd06f6dff149e67b60c4cd083bfea8
- https://git.kernel.org/stable/c/78aad93e938f013d9272fe0ee168f27883afa95c
- https://git.kernel.org/stable/c/81c7a3c22a0f2808cf4ae0b4908f59763b23606d
- https://git.kernel.org/stable/c/9d20d48be2c4a071fb015eb09bda2cecd25daf34
- https://git.kernel.org/stable/c/c1bb9336ae6b54a5f6a353c4bd4ed9a4307e429b
- https://git.kernel.org/stable/c/c85cff648a2bc92322912db5f1727ad05afae7b6
- https://git.kernel.org/stable/c/e2d19969c8d9198ecc3090bcd5312ecd503a3339
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_uart: fix UAFs and race conditions in close and init paths\n\nVulnerabilities leading to Use-After-Free (UAF) and Null Pointer\nDereference (NPD) conditions were observed in the lifecycle management\nof hci_uart.\n\nThe primary issue arises because the workqueues (init_ready and\nwrite_work) are only flushed/cancelled if the HCI_UART_PROTO_READY\nflag is set during TTY close. If a hangup occurs before setup completes,\nhci_uart_tty_close() skips the teardown of these workqueues and\nproceeds to free the `hu` struct. When the scheduled work executes\nlater, it blindly dereferences the freed `hu` struct.\n\nFurthermore, several data races and UAFs were identified in the teardown\nsequence:\n1. Calling hci_uart_flush() from hci_uart_close() without effectively\n disabling write_work causes a race condition where both can concurrently\n double-free hu->tx_skb. This happens because protocol timers can\n concurrently invoke hci_uart_tx_wakeup() and requeue write_work.\n2. Calling hci_free_dev(hdev) before hu->proto->close(hu) causes a UAF\n when vendor specific protocol close callbacks dereference hu->hdev.\n3. In the initialization error paths, failing to take the proto_lock\n write lock before clearing PROTO_READY leads to races with active\n readers. Additionally, hci_uart_tty_receive() accesses hu->hdev\n outside the read lock, leading to UAFs if the initialization error\n path frees hdev concurrently.\n\nFix these synchronization and lifecycle issues by:\n1. Re-ordering hci_uart_tty_close() to clear HCI_UART_PROTO_READY first,\n followed immediately by a cancel_work_sync(&hu->write_work). Clearing\n the flag locks out concurrent protocol timers from successfully invoking\n hci_uart_tx_wakeup(), effectively rendering the cancellation permanent\n and preventing the tx_skb double-free.\n2. Note: Clearing PROTO_READY early causes hci_uart_close() to skip\n hu->proto->flush(). This is perfectly safe in the tty_close path\n because hu->proto->close() executes shortly after, which intrinsically\n purges all protocol SKB queues and tears down the state.\n3. Relocating hu->proto->close(hu) strictly prior to hci_free_dev(hdev)\n across all close and error paths to prevent vendor-level UAFs.\n4. Moving the hdev->stat.byte_rx increment in hci_uart_tty_receive()\n inside the proto_lock read-side critical section to safely synchronize\n with device unregistration.\n5. Adding cancel_work_sync(&hu->write_work) to hci_uart_close() to safely\n flush the workqueue before hci_uart_flush() is invoked via the HCI core.\n6. Utilizing cancel_work_sync() instead of disable_work_sync() across\n all paths to prevent permanently breaking user-space retry capabilities."
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"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nBluetooth: hci_uart: corrige UAFs y condiciones de carrera en las rutas de cierre e inicialización\n\nSe observaron vulnerabilidades que conducen a condiciones de Uso Después de Liberación (UAF) y Desreferencia de Puntero Nulo (NPD) en la gestión del ciclo de vida de hci_uart.\n\nEl problema principal surge porque las colas de trabajo (workqueues) (init_ready y write_work) solo se vacían/cancelan si la bandera HCI_UART_PROTO_READY está establecida durante el cierre de TTY. Si ocurre un cuelgue antes de que se complete la configuración, hci_uart_tty_close() omite la desinstalación de estas colas de trabajo y procede a liberar la estructura 'hu'. Cuando el trabajo programado se ejecuta más tarde, desreferencia ciegamente la estructura 'hu' liberada.\n\nAdemás, se identificaron varias condiciones de carrera de datos y UAFs en la secuencia de desinstalación:\n1. Llamar a hci_uart_flush() desde hci_uart_close() sin deshabilitar efectivamente write_work causa una condición de carrera donde ambos pueden liberar doblemente hu->tx_skb de forma concurrente. Esto sucede porque los temporizadores del protocolo pueden invocar concurrentemente hci_uart_tx_wakeup() y volver a encolar write_work.\n2. Llamar a hci_free_dev(hdev) antes de hu->proto->close(hu) causa un UAF cuando las devoluciones de llamada de cierre del protocolo específico del proveedor desreferencian hu->hdev.\n3. En las rutas de error de inicialización, no tomar el bloqueo de escritura proto_lock antes de borrar PROTO_READY conduce a condiciones de carrera con lectores activos. Además, hci_uart_tty_receive() accede a hu->hdev fuera del bloqueo de lectura, lo que lleva a UAFs si la ruta de error de inicialización libera hdev concurrentemente.\n\nCorregir estos problemas de sincronización y ciclo de vida mediante:\n1. Reordenar hci_uart_tty_close() para borrar HCI_UART_PROTO_READY primero, seguido inmediatamente por un cancel_work_sync(&hu->write_work). Borrar la bandera bloquea a los temporizadores del protocolo concurrentes para que no invoquen con éxito hci_uart_tx_wakeup(), haciendo que la cancelación sea permanente y evitando la doble liberación de tx_skb.\n2. Nota: Borrar PROTO_READY temprano hace que hci_uart_close() omita hu->proto->flush(). Esto es perfectamente seguro en la ruta tty_close porque hu->proto->close() se ejecuta poco después, lo que intrínsecamente purga todas las colas SKB del protocolo y desinstala el estado.\n3. Reubicar hu->proto->close(hu) estrictamente antes de hci_free_dev(hdev) en todas las rutas de cierre y error para prevenir UAFs a nivel de proveedor.\n4. Mover el incremento de hdev->stat.byte_rx en hci_uart_tty_receive() dentro de la sección crítica del lado de lectura de proto_lock para sincronizar de forma segura con la anulación del registro del dispositivo.\n5. Añadir cancel_work_sync(&hu->write_work) a hci_uart_close() para vaciar de forma segura la cola de trabajo antes de que hci_uart_flush() sea invocado a través del núcleo HCI.\n6. Utilizar cancel_work_sync() en lugar de disable_work_sync() en todas las rutas para evitar romper permanentemente las capacidades de reintento del espacio de usuario."
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"lastModified": "2026-07-23T07:10:00.113",
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