Bug 2517033 (CVE-2026-74551)

Summary: CVE-2026-74551 kernel: hwmon: (nzxt-smart2) DMA-align output buffer
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `hwmon: (nzxt-smart2)` driver. This vulnerability allows for immediate and deterministic memory corruption on systems with non-coherent CPU architectures, such as ARM or MIPS. When operations like setting a fan speed or updating an interval trigger a USB Direct Memory Access (DMA) mapping, the DMA process can corrupt adjacent variables due to cacheline sharing. This issue is resolved by aligning the output buffer to prevent unintended data corruption.
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Description OSIDB Bzimport 2026-08-15 12:46:04 UTC 
In the Linux kernel, the following vulnerability has been resolved:

hwmon: (nzxt-smart2) DMA-align output buffer

Sashiko reports:

When send_output_report() calls hid_hw_output_report(), the underlying USB
HID core calls usb_interrupt_msg() which maps this buffer directly for DMA.

When the DMA mapping flushes or invalidates the cacheline, it will corrupt
the adjacent variables (mutex, update_interval) that were modified
concurrently by the CPU. This causes memory corruption due to cacheline
sharing on non-coherent CPU architectures (such as ARM or MIPS). The DMA
API debugging tool (CONFIG_DMA_API_DEBUG) will trigger runtime warnings
for this violation.

Any operation that triggers send_output_report() (like setting a fan speed
or updating the interval) causes the USB DMA mapping. On systems with
non-coherent caches, this structural bug causes immediate and deterministic
memory corruption.

Align the output buffer to ARCH_DMA_MINALIGN to fix the problem.
Comment 1 Mauro Matteo Cascella 2026-08-19 18:58:20 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081550-CVE-2026-74551-720e@gregkh/T