Advisory [CVE-2026-64135] (pmbus/adm1266) widen blackbox-info buffer to I2C_SMBUS_BLOCK_MAX

In the Linux kernel, the following vulnerability has been resolved: hwmon: (pmbus/adm1266) widen blackbox-info buffer to I2C_SMBUS_BLOCK_MAX adm1266_nvmem_read_blackbox() declares a 5-byte stack buffer and passes it to i2c_smbus_read_block_data() to retrieve the 4-byte BLACKBOX_INFO response. i2c_smbus_read_block_data() does not honour caller buffer sizes -- it memcpy()s data.block[0] bytes from the SMBus transaction (where data.block[0] is the length byte returned by the slave device, up to I2C_SMBUS_BLOCK_MAX = 32): memcpy(values, &data.block[1], data.block[0]); If the device returns any block length above 5, the call overflows the caller's 5-byte stack buffer before the post-call if (ret!= 4) return -EIO; check has a chance to reject the response.

Widen the local buffer to I2C_SMBUS_BLOCK_MAX so the helper has room for any well-formed SMBus block response, matching the convention used by the other i2c_smbus_read_block_data() callers in this driver.

This vulnerability occurs because the adm1266_nvmem_read_blackbox() function uses a small, fixed-size buffer to read data from an I2C (Inter-Integrated Circuit) device. If the device sends more data than the buffer can hold, it causes a buffer overflow.

A local attacker could exploit this flaw to trigger a denial of service (DoS) or potentially escalate their privileges on the system. Red Hat severity: not rated.