CVE-2026-17053 Missing authorization in zephyr
Unprivileged users can manipulate kernel SMBus callbacks, causing denial of service or address disclosure via unvalidated pointers in Zephyr RTOS.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-17053?
CVE-2026-17053 is a medium-severity missing authorization vulnerability in zephyrproject zephyr, published on 1 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-862
Which versions are affected by CVE-2026-17053?
How do I fix CVE-2026-17053?
No fix has been published for CVE-2026-17053 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-17053 being exploited?
There is no known exploitation of CVE-2026-17053 in the wild and no public exploit code.
Sources
Also known as GHSA-hqh5-956f-5x2r.