Zephyrproject Zephyr Submission Queue Verifier rtio_syscalls.c rtio_vrfy_sqe permission

Summaryinfo

A vulnerability was found in Zephyrproject Zephyr. It has been classified as very critical. This impacts the function rtio_vrfy_sqe of the file subsys/rtio/rtio_syscalls.c of the component Submission Queue Verifier. The manipulation leads to permission. This vulnerability is uniquely identified as CVE-2026-87041. Local access is required to approach this attack. No exploit exists.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Zephyrproject Zephyr (unknown version). This issue affects the function rtio_vrfy_sqe of the file subsys/rtio/rtio_syscalls.c of the component Submission Queue Verifier. The manipulation with an unknown input leads to a permission vulnerability. Using CWE to declare the problem leads to CWE-275. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-87041 since 09/08/2026. The exploitation is known to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/04/2026). The attack technique deployed by this issue is T1222 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Project Management Software

Vendor

• Zephyrproject

Name

• Zephyr

CPE 2.3info

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CPE 2.2info

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