CVE-2026-45865: mctp i2c: initialise event handler read bytes

CVE-2026-45865: mctp i2c: initialise event handler read bytes

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2026-45865 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 6.1.165 with commit 93e01e837e105299f1c259ef71f6e1ec4fe806e3
	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 6.6.128 with commit 11f83253244060b5de5eac787f61ae3f3e559d01
	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 6.12.75 with commit fa9861e5c8af7651dddfa8d490aaada17ae33b6c
	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 6.18.14 with commit 6ff2ebfef75fbc57d937d8fbe738b967edf2d331
	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 6.19.4 with commit 1eeedb310229bfee9dd4d992e5bba33fe1378a8f
	Issue introduced in 5.18 with commit f5b8abf9fc3dacd7529d363e26fe8230935d65f8 and fixed in 7.0 with commit 2a14e91b6d76639dac70ea170f4384c1ee3cb48d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-45865
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/net/mctp/mctp-i2c.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/93e01e837e105299f1c259ef71f6e1ec4fe806e3
	https://git.kernel.org/stable/c/11f83253244060b5de5eac787f61ae3f3e559d01
	https://git.kernel.org/stable/c/fa9861e5c8af7651dddfa8d490aaada17ae33b6c
	https://git.kernel.org/stable/c/6ff2ebfef75fbc57d937d8fbe738b967edf2d331
	https://git.kernel.org/stable/c/1eeedb310229bfee9dd4d992e5bba33fe1378a8f
	https://git.kernel.org/stable/c/2a14e91b6d76639dac70ea170f4384c1ee3cb48d