CVE-2026-80975
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel, a vulnerability exists in the mfd: qnap-mcu driver. The qnap_mcu_exec() function publishes an on-stack buffer (rx) to the receive path, which can write to it after a command timeout or write failure when the stack frame is no longer valid. This leads to stack memory corruption and potential arbitrary code execution.
Risk Assessment
The vulnerability can cause kernel memory corruption, system crash, or privilege escalation by a local attacker. In environments with access to the QNAP MCU device, the risk is high.
Recommendation
Update the Linux kernel to a version containing the fix that moves the receive buffer into the qnap_mcu structure. If updating is not possible, restrict access to devices using this driver.
Other vulnerabilities in Linux kernel
See all- CVE-2026-99259Unknown
In the Linux kernel, the soc/tegra: pmc driver has an uninitialised early_pmc->rate variable for legacy 32-bit Tegra devices. The variable is never configured and remains 0, triggering a warning in tegra_pmc_enter_suspend_mode(). The issue appeared after the PMC driver was changed to create the PMC context dynamically, updating rate only in the new context.
- CVE-2026-99258Unknown
In the Linux kernel, hv_apicid_to_vp_index() uses per-CPU hypercall input and output pages. In an SEV-SNP CoCo VM without a paravisor the output page is not allocated, so the hypervisor stores the resulting VP index into memory not allocated by the guest. The fix uses the input page for both input and output.
- CVE-2026-99257Unknown
In the Linux kernel, the shared GPIO mechanism based on platform lookup tables requires an associated struct device. An fwnode-based lookup with no associated device currently causes a NULL-pointer dereference. The fix adds a check that lets the kernel gracefully handle this situation with an error.
- CVE-2026-99256Unknown
In the Linux kernel, the dm cache module used a rw_semaphore for background_work_lock, although write locks on rw_semaphores have strict owner semantics. The locking process was not always the same as the unlocking one, triggering a warning with CONFIG_DEBUG_RWSEMS during suspend/resume of a cache device. The fix replaces the rw_semaphore with a spinlock and a wait queue.
- CVE-2026-99251Unknown
In the Linux kernel, init_vp_index() contains a retry loop that strips CPUs from a node if they are already in the allocated cpumask or outside the HK_TYPE_MANAGED_IRQ housekeeping cpumask. If the housekeeping cpumask contains no CPU in that node, the loop becomes infinite. The fix skips NUMA nodes with no housekeeping CPU and aborts early when no online housekeeping CPUs exist.
- CVE-2026-99250Unknown
In the Linux kernel, the NBCON console printing kthreads are started very early during boot via early_initcall(). Asynchronously enabling/disabling interrupts during early boot may interfere with early SMP setup on some hardware platforms, causing hangs. The fix postpones kthread startup until after all arch initcalls have completed.
- CVE-2026-99249Unknown
In the Linux kernel, zap_pid_ns_processes() waiting for PID namespace cleanup was not freezable. A tracer outside the namespace that does not reap its traced zombies keeps PIDs allocated, making the wait unbounded and causing every suspend attempt to fail. The fix makes the wait loops use TASK_FREEZABLE states so the freezer can freeze waiting tasks.
- CVE-2026-99248Unknown
In the Linux kernel, the i2c: xiic driver was changed to restore non-managed runtime PM instead of the devres-based approach to fix a clk WARN flood. The managed release tore down runtime PM in the wrong order, causing the clock to be disabled twice and triggering "clkN already disabled" warnings on every teardown.
- CVE-2026-99247Unknown
In the Linux kernel, if trace buffer allocation fails during early boot, tracing_disabled remains set and the global trace array events list stays uninitialized. tracer_init_tracefs_work_func() runs asynchronously without checking this state and calls event_trace_init() and init_tracer_tracefs(), leading to a NULL pointer dereference Oops during boot. The fix checks tracing_disabled at the start of the work function.
- CVE-2026-99215Unknown
In the Linux kernel power supply subsystem, a use-after-free vulnerability exists. If a power supply is unregistered while its external_power_changed() callback is still running, the driver may free data that the callback is still accessing, leading to a kernel crash (NULL pointer dereference).
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: mfd: qnap-mcu: keep the reply buffer alive past a command timeout qnap_mcu_exec() publishes an on-stack buffer to the receive path: unsigned char rx[QNAP_MCU_RX_BUFFER_SIZE]; ... reply->data = rx; reply->length = length; and qnap_mcu_receive_buf() writes into it from the serdev receive path, which runs out of flush_to_ldisc() and is not serialized against qnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec() holds that mutex across wait_for_completion_timeout(). On a timeout qnap_mcu_exec() returns with reply->data still pointing at its own frame. A reply that arrives late, or an unsolicited message from the MCU, is then written into a stack frame that has been left, corrupting whatever runs next on that stack. The same applies when qnap_mcu_write() fails, since that path returns without touching the reply state either. Move the receive buffer into struct qnap_mcu. It is 37 bytes and the structure is devm_kzalloc()ed, so it lives as long as the driver, and a late write lands in memory that is still valid and is reinitialized by the next command. bus_lock keeps commands from sharing it. This deliberately does not clear reply->data or reply->length on the timeout path. Doing so races with qnap_mcu_receive_buf(), which reads both after its if (!reply->length) return size; check: clearing reply->data gives a NULL dereference, and clearing reply->length alone removes the reply->received == reply->length exit condition, so the copy loop runs until the uart chunk is consumed and overruns the buffer. Leaving both set keeps the write bounded by reply->length, which qnap_mcu_exec() has already checked against sizeof(mcu->rx).
Vulnerability data from NVD (NIST) · CISA KEV · EPSS