ZephyrProject Zephyr up to 4.4.1 SMBus Driver API smbus_handlers.c cb input validation

Summaryinfo

A vulnerability described as very critical has been identified in ZephyrProject Zephyr up to 4.4.1. The affected element is the function smbus_smbalert_remove_cb/smbus_host_notify_remove_cb of the file drivers/smbus/smbus_handlers.c of the component SMBus Driver API. The manipulation of the argument cb results in input validation. This vulnerability is cataloged as CVE-2026-17053. The attack must be initiated from a local position. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as very critical has been found in ZephyrProject Zephyr up to 4.4.1. Affected is the function smbus_smbalert_remove_cb/smbus_host_notify_remove_cb of the file drivers/smbus/smbus_handlers.c of the component SMBus Driver API. The manipulation of the argument cb with an unknown input leads to a input validation vulnerability. CWE is classifying the issue as CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

The SMBus driver API exposed smbus_smbalert_remove_cb() and smbus_host_notify_remove_cb() as Zephyr syscalls. Their verifiers in drivers/smbus/smbus_handlers.c validated only the dev argument with K_SYSCALL_OBJ(dev, K_OBJ_DRIVER_SMBUS) and forwarded the caller-supplied struct smbus_callback *cb pointer into kernel-mode driver code without any K_SYSCALL_MEMORY_READ/K_SYSCALL_MEMORY_WRITE validation. A companion change in 2023 had already removed the matching smbus_smbalert_set_cb() / smbus_host_notify_set_cb() syscalls for this reason, but the two removal syscalls were left exposed. On a build with CONFIG_USERSPACE=y, CONFIG_SMBUS=y and a driver implementing the callback operations (drivers/smbus/intel_pch_smbus.c with CONFIG_SMBUS_INTEL_PCH_SMBALERT/CONFIG_SMBUS_INTEL_PCH_HOST_NOTIFY, or drivers/smbus/smbus_stm32.c with CONFIG_SMBUS_STM32_SMBALERT), any user-mode thread that has been granted the SMBus device object can invoke these syscalls with an arbitrary pointer. The value reaches smbus_callback_remove() in drivers/smbus/smbus_utils.h, which uses it as a node identity against the kernel's sys_slist_t of registered callbacks. The consequence is that an unprivileged thread can unregister an SMBALERT or Host Notify callback that a supervisor-mode component registered, silently disabling alert handling for the rest of the system; because Zephyr images have fixed symbol addresses and the syscall returns 0 on a hit versus -ENOENT on a miss, the target address is both derivable and searchable. In builds with CONFIG_ASSERT=y the __ASSERT(callback->handler, ...) check additionally dereferences the caller-supplied address in supervisor mode, so a bogus pointer raises a kernel-mode fault and a fatal system error, and the fault/no-fault outcome discloses which addresses are mapped. The fix removes both syscall entry points, demoting the two functions to ordinary static inline calls so that callback list manipulation is available only to supervisor-mode code. There is no impact on builds without CONFIG_USERSPACE, and no impact on configurations that do not enable an SMBus driver with SMBALERT or Host Notify support.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-17053 since 07/24/2026. The exploitability is told to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/01/2026).

Upgrading to version 4.4.2 eliminates this vulnerability. Applying the patch 331df881a8b8cb4296699a8251c9fd74a4308f3d is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Project Management Software

Vendor

• ZephyrProject

Name

• Zephyr

Version

• 4.4.0
• 4.4.1

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CPE 2.2info

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