CVE-2025-38217 is a medium severity vulnerability in the Linux kernel's hwmon subsystem affecting the fts_read() function. It involves a Time-of-Check to Time-of-Use (TOCTOU) race condition due to unsynchronized access to a shared variable, which can lead to undefined behavior such as kernel crashes. The issue arises when the variable data->fan_source[channel] is checked and then used without locking, allowing concurrent modification by another thread. The vulnerability has been fixed by reading the variable once into a local variable and adding bounds checking before bit shifting.