CVE-2026-89621: HID: mcp2221: validate report size in mcp2221_raw_event()

CVE-2026-89621: HID: mcp2221: validate report size in mcp2221_raw_event()

[Greg Kroah-Hartman]

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

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

In the Linux kernel, the following vulnerability has been resolved:

HID: mcp2221: validate report size in mcp2221_raw_event()

mcp2221_raw_event() never validates the size of incoming HID reports.
In the MCP2221_I2C_GET_DATA path it trusts the device-supplied data[3]
as the copy length without checking that 4 + data[3] bytes actually
exist in the received report. A malicious or misbehaving USB device can
send a short report with a large data[3], causing the memcpy to read
past the valid report data in the HID transfer buffer and leak
uninitialized kernel memory back to userspace through the I2C/SMBus
read path.

Add a minimum size check at entry and validate that the source range
fits within the received report before the copy.

The Linux kernel CVE team has assigned CVE-2026-89621 to this issue.


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

	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 6.12.109 with commit bdc6a3af0dd734a326acdb7d6401a3b6a9f4f149
	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 6.18.50 with commit 127de5919820f88a9d55e8371ad4ac49f625f4c5
	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 7.2.4 with commit 7c18fb36708a97ff6772825cc087b6d537bbf0d5
	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 7.3-rc1 with commit 2c9a6998c19503626c57a2267bf279e204113079

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-2026-89621
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/hid/hid-mcp2221.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/bdc6a3af0dd734a326acdb7d6401a3b6a9f4f149
	https://git.kernel.org/stable/c/127de5919820f88a9d55e8371ad4ac49f625f4c5
	https://git.kernel.org/stable/c/7c18fb36708a97ff6772825cc087b6d537bbf0d5
	https://git.kernel.org/stable/c/2c9a6998c19503626c57a2267bf279e204113079