The Linux kernel hwmon driver for pmbus/adm1266 used a fixed 5-byte stack buffer in adm1266_nvmem_read_blackbox() to read SMBus block data via i2c_smbus_read_block_data(). However, i2c_smbus_read_block_data() copies the number of bytes indicated by the device's length byte, which can be up to I2C_SMBUS_BLOCK_MAX (32 bytes). This mismatch allows a stack buffer overflow if the device returns more than 5 bytes. The vulnerability was resolved by increasing the local buffer size to I2C_SMBUS_BLOCK_MAX, aligning with the SMBus protocol and other driver usage.

A stack buffer overflow in the Linux kernel hwmon pmbus/adm1266 driver could potentially lead to memory corruption. The description does not specify exploitation details or impact beyond the overflow condition. No known exploits in the wild have been reported.

A fix has been implemented in the Linux kernel by widening the buffer to I2C_SMBUS_BLOCK_MAX. Users should update to a kernel version that includes this fix. Since this is a kernel vulnerability, applying the official kernel update or patch that addresses CVE-2026-64135 is the recommended remediation. Patch status is not explicitly confirmed in the provided data; users should verify with the vendor or kernel maintainers for the specific fixed versions.