The Linux kernel's MTD mchp23k256 driver determines a flash chip's capacity by consulting the OF match table or the SPI id table. During probe, the driver mistakenly falls back to a hard‑coded capacity when the device is detected via a non‑OF SPI modalias, even if the SPI id table specifies a different part. As a result, the kernel may configure an incorrect geometry for the flash device, causing read/write operations to overshoot the actual storage area. This can overwrite adjacent memory or corrupt data, potentially leading to system instability or firmware failure.

The flaw exists in the Linux kernel wherever the mchp23k256 MTD driver is compiled, affecting all kernel versions prior to the patch that replaces of_device_get_match_data() with spi_get_device_match_data(). The driver is part of the mainline kernel and is used in many embedded boards and IoT devices. No specific version numbers are listed, so any installation that includes this driver is impacted until updated.

The vulnerability has no EPSS score or KEV listing, and CVSS is not provided. The likely attack vector is local or physical access to the SPI bus to influence the match data used by the driver. Based on the description, it is inferred that an attacker who can inject a custom SPI id‑table entry or manipulate the modalias may force the driver to install an incorrect flash geometry. This could corrupt data or crash the system, though it does not directly enable arbitrary code execution. No public exploits are noted, but the weakness is potentially exploitable in devices that rely on the mchp23k256 driver.