CVE-2026-45865: mctp i2c: initialise event handler read bytes
In the Linux kernel, the following vulnerability has been resolved:
mctp i2c: initialise event handler read bytes
Set a 0xff value for i2c reads of an mctp-i2c device. Otherwise reads will return "val" from the i2c bus driver. For i2c-aspeed and i2c-npcm7xx that is a stack uninitialised u8.
Tested with "i2ctransfer -y 1 r10@0x34" where 0x34 is a mctp-i2c instance, now it returns all 0xff.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Set read bytes for i2c accesses of an mctp-i2c device to 0xff (e.g., so an i2ctransfer read such as r10@0x34 where 0x34 is an mctp-i2c instance returns all 0xff instead of uninitialized stack bytes).
Linux kernel mctp-i2c i2c read value for mctp-i2c device = 0xff - Compensating control
Verify the fix by testing with i2ctransfer, e.g., run "i2ctransfer -y 1 r10@0x34" where 0x34 is an mctp-i2c instance, and confirm the read returns all 0xff.