missing range checks for eeprom_len being valid.

missing range check for header->header1.len being valid.

uint32_t pkglen

if (pkglen > (MCLBYTES - ETHER_ALIGN - IEEE80211_CRC_LEN ))

xxx error;

Remove this KASSERT() - we don't want to panic on corrupt USB data!

Please add checks here for frame_start wrapping around.

The for-loop condition should read: (offset + sizeof(*uc)) <= fw->datasize

Else you might read data which is not inside the BRA.

Same here.

Please also add this check:

if (sizeof(struct upgt_fw_bra_option) > (size_t)(fw->datasize - offset) ||
    (bra_option_len > (size_t)(fw->datasize - offset - sizeof(struct upgt_fw_bra_option)))

IMHO, this code path will never work: typically error handling duplicates USB_ST_TRANSFERRED event with non-zero status code passed to ieee80211_tx_complete().
Here 1) mbuf is not freed - memory leak? 2) data buffer is not moved from active to inactive ring, so Tx will stop.