Linux Kernel EUVD-2026-55417

The ethosu driver in the Linux kernel provides a userspace interface to Arm Ethos-U neural processing unit (NPU) accelerator hardware, used in embedded and edge ML inference workloads. The driver is responsible for validating command streams submitted by userspace before forwarding them to the accelerator, acting as a security boundary between untrusted user input and privileged kernel memory operations. The vulnerability resides in the element-size accounting logic of this validation step. For tensors laid out in NHWC (N×Height×Width×Channel) format, the element size factor is entirely omitted from the computed size, so the validator approves buffers that are far smaller than the actual data. Independently, the driver uses a single bitfield decode for element precision across all tensor types, but the hardware encoding differs: IFM and IFM2 input tensors store precision in bits 2:3, while OFM output tensors use bits 1:2 - causing the driver to extract a wrong precision value for OFM tensors, compounding the underestimation for 16-, 32-, and 64-bit element widths. No formal CWE has been assigned, but the root cause class corresponds to CWE-682 (Incorrect Calculation) or CWE-131 (Incorrect Calculation of Buffer Size), resulting in insufficient input validation at a kernel trust boundary. Affected CPE: cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*.