The user-mode verifier for the peci_transfer() system call, z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the device object permission and copied the caller-supplied struct peci_msg with k_usermode_from_copy(). That copy validates the outer structure only; the buf pointers and len values inside the embedded struct peci_buf members tx_buffer and rx_buffer remained fully caller-controlled and were passed unchecked to the driver. Every in-tree PECI driver dereferences those pointers in supervisor mode: peci_npcx_transfer() in drivers/peci/peci_npcx.c and peci_it8xxx2_transfer() in drivers/peci/peci_ite_it8xxx2.c copy hardware bytes into rx_buffer.buf[i] and read command bytes out of tx_buffer.buf[i], and peci_xec_read()/peci_xec_write() in drivers/peci/peci_mchp_xec.c…