CVE-2026-89621

What the bug is

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.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/hid/hid-mcp2221.c

What this is

MCP2221A MICROCHIP USB-HID TO I2C BRIDGE DRIVERMAINTAINERS section matched on drivers/hid/hid-mcp2221.c · linux-i2c@vger.kernel.org · Maintained

Kernel module

hid_mcp2221

Check it on the machine

grep -wE 'CONFIG_HID|CONFIG_HID_MCP2221|CONFIG_HID_SUPPORT' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w hid_mcp2221

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64

M

a module where it is built at all; some flavours do not build it

Build switches

CONFIG_HID, CONFIG_HID_MCP2221, CONFIG_HID_SUPPORT

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-11 (37 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.22%, higher than 11.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/hid

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.7	5.10.270	cb38b1f149b7
5.7	5.15.221	b2c67dc0e30c
5.7	6.1.188	fffcfa367072
5.7	6.6.157	c1c508e89239
5.7	6.12.109	bdc6a3af0dd7
5.7	6.18.50	127de5919820
5.7	7.2.4	7c18fb36708a
5.7	7.3	2c9a6998c195

Debian advisories