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CVE-2026-16513
The userspace verifier z_vrfy_rtio_sqe_copy_in_get_handles() in subsys/rtio/rtio_syscalls.c (subsys/rtio/rtio_handlers.c before v4.3.0) validated the RTIO object handle and the sqes input array, but not the handle out-parameter. On the first loop iteration it executed *handle = sqe, storing the kernel address of the newly acquired submission-queue entry through a pointer taken verbatim from user mode, with no K_SYSCALL_MEMORY_WRITE check in front of it.
Any user-mode thread that has been granted a struct rtio kernel object can invoke the syscall with an arbitrary address in handle. That is the ordinary way an unprivileged thread uses the RTIO API, for example via sensor_read_async_mempool() or the async ADC helpers, which call rtio_sqe_copy_in_get_handles() internally. The store happens in supervisor mode before any submission-entry validation, so it fires regardless of whether the SQE contents are subsequently rejected. Only builds with CONFIG_USERSPACE and CONFIG_RTIO are affected; without CONFIG_USERSPACE the verifier is not compiled and the caller is already privileged.
The write address is fully attacker-chosen and the written value is a pointer into the caller's own RTIO ring, whose contents the caller controls (the following *sqe = sqes[i] copies an attacker-supplied struct rtio_sqe into that slot). This yields a write-what-where primitive placing a pointer to attacker-controlled data at any kernel address, sufficient to corrupt kernel function pointers, thread structures, or memory-domain partition tables, and thus to escalate from user mode to kernel mode, defeating the isolation boundary CONFIG_USERSPACE is meant to enforce. At minimum it is a reliable kernel memory-corruption and crash primitive. The reporter reproduced the write on qemu_x86: a K_USER thread changed a supervisor global from NULL to a live kernel SQE pointer.
The fix adds K_SYSCALL_MEMORY_WRITE(handle, sizeof(*handle)) (guarded by the existing optional-NULL semantics) before the loop, so the destination must lie in the calling thread's writable memory domain or the thread is terminated by K_OOPS. The neighbouring verifier z_vrfy_rtio_cqe_get_mempool_buffer(), which checked its buff/buff_len out-parameters only for read although the implementation writes through them, was hardened separately by bea93400138 ("rtio: syscalls: validate output params as writable"); that residual was materially weaker, since a read check still confines the target to the caller's own memory domain.
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The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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