CVE-2026-87041 Verificación invertida de permisos de memoria en el verificador de syscalls RTIO permite a un hilo de modo…
El verificador de la cola de envío RTIO, rtio_vrfy_sqe(), acumulaba los resultados de K_SYSCALL_MEMORY() en su indicador valid_sqe con &=, por lo que cada verificación de permisos de búfer aportaba lo contrario de su resultado. Una solicitud con un puntero tx.buf, rx.buf o txrx.tx_buf/txrx.rx_buf no accesible para el hilo llamador era aceptada, mientras que un búfer legítimo del hilo provocaba que el hilo llamador fuera terminado con un oops del kernel. El verificador se ejecuta en nombre de la syscall…
CVSS 3.1
- Probabilidad de explotación · EPSS del 09/110,1 % · percentil 1
- Explotada activamenteNo confirmada
- Exploit públicoNo conocido
Afectados
zephyrproject zephyr
desde 3.3.0 hasta antes de 4.3.2desde 4.4.0 hasta antes de 4.5.0
Qué hacer
- Verificá si usás zephyr y en qué versión.
- Actualizá a la versión corregida que indique el fabricante en su aviso o aplicá su mitigación.
- Revisá registros y accesos de los sistemas expuestos para descartar un uso previo.
Calculadora CVSS
CVSS 3.1 · 7.8 ALTA
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Vector de ataqueLocal
- Complejidad del ataqueBaja
- Privilegios requeridosBajos
- Interacción del usuarioNinguna
- AlcanceSin cambio
- ConfidencialidadAlta
- IntegridadAlta
- DisponibilidadAlta
Descripción original
The RTIO submission-queue verifier rtio_vrfy_sqe() in subsys/rtio/rtio_syscalls.c (subsys/rtio/rtio_handlers.c before v4.3.0) accumulated the results of K_SYSCALL_MEMORY() into its valid_sqe flag with &=. That macro returns nonzero on failure (it is built on K_SYSCALL_VERIFY_MSG(), which yields !(expr)), so every buffer permission check contributed the opposite of its result. A submission whose tx.buf, rx.buf or txrx.tx_buf/txrx.rx_buf pointer was not accessible to the calling thread was accepted, while a legitimate, thread-owned buffer caused the calling thread to be killed with a kernel oops.
The verifier runs on behalf of the rtio_sqe_copy_in_get_handles() system call (also reached through the inline rtio_sqe_copy_in() wrapper), so it is driven directly by untrusted user-mode input on any image built with CONFIG_USERSPACE. A user thread that has been granted an RTIO context and an rtio_iodev object — the intended usage of RTIO userspace support, established via rtio_access_grant() — can submit an SQE whose buffer pointer and length name arbitrary kernel memory; the object check on sqe->iodev is unaffected and still passes, and the crafted SQE is forwarded to the bus driver unchanged.
Downstream consumers dereference the pointer with supervisor privilege. The generic I2C and I3C RTIO fallback handlers (drivers/i2c/i2c_rtio_default.c, drivers/i3c/i3c_rtio_default.c) copy sqe.rx.buf/sqe.tx.buf into struct i2c_msg and call i2c_transfer(), and the vendor SPI/I2C RTIO drivers behave equivalently. An RTIO_OP_RX submission therefore has peripheral data written into kernel memory of the attacker's choosing (arbitrary kernel write), an RTIO_OP_TX submission clocks kernel memory out over the bus (kernel memory disclosure), and a pointer to unmapped memory faults the kernel. This is a full escape from the user-mode isolation boundary that CONFIG_USERSPACE exists to enforce.
The defect was masked for years because the in-tree user-mode RTIO tests only exercise RTIO_OP_NOP and mempool-backed reads, neither of which reaches the affected checks. The fix negates each K_SYSCALL_MEMORY() result and additionally validates the TXRX transmit buffer read-only, matching the SPI, I2C and I3C handlers.
Referencias (2)
Resumen traducido automáticamente de la descripción original. Fuente: Nureq Monitor. Cómo funciona.