Off-by-One Error in I/O Handling in Linux Kernel by Vendor

CVE-2026-89751

What is CVE-2026-89751?

The Linux Kernel has been identified with an off-by-one error in the port I/O handling mechanism in functions handle_in() and handle_out(). This programming flaw occurs due to a miscalculation in the bit mask for I/O sizes, resulting in the generation of an incorrect mask that is one bit too wide for all I/O operations. Specifically, when handling input for size=1 using INB, the mask produced is 0x1FF instead of the expected 0xFF, potentially leading to unauthorized access to bits beyond the intended data range.

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