CVE-2026-64339

What the bug is

usbio_bulk_msg() copies bpkt_len = le16_to_cpu(bpkt->len) bytes out of the bulk IN buffer (usbio->rxbuf, allocated with size usbio->rxbuf_len) into the caller's buffer. bpkt_len is fully controlled by the device and is only checked against ibuf_len; ibuf_len in turn is checked against usbio->txbuf_len, not against rxbuf_len: if ((obuf_len > (usbio->txbuf_len - sizeof(*bpkt))) || (ibuf_len > (usbio->txbuf_len - sizeof(*bpkt)))) return -EMSGSIZE; txbuf_len and rxbuf_len are taken independently from the bulk OUT and bulk IN endpoint wMaxPacketSize in usbio_probe(). A malicious or malfunctioning device that advertises a large bulk OUT endpoint and a small bulk IN endpoint (e.g. by claiming one of the quirk-free IDs such as the Lattice NX33U, 0x2ac1:0x20cb) therefore makes ibuf_len, and hence the device-supplied bpkt_len, exceed rxbuf_len. memcpy() then reads up to txbuf_len - rxbuf_len bytes past the end of the rxbuf slab object. The over-read bytes are handed back to the i2c layer and on to user space through i2c-dev, disclosing adjacent slab memory; with KASAN this is reported as a slab-out-of-bounds read. The number of bytes actually received is already known: act equals the URB actual_length and is bounded by rxbuf_len. Reject any response that claims more payload than was received, mirroring the existing "act < sizeof(*bpkt)" check just above. The control path (usbio_ctrl_msg()) is not affected: it uses a single buffer (ctrlbuf) for both directions, so its analogous copy can never leave the allocation. Found by code review. The out-of-bounds read was confirmed under AddressSanitizer with a faithful userspace model of usbio_bulk_msg()'s receive path (an rxbuf_len-sized buffer, the same act/ibuf_len/bpkt_len checks and the memcpy). A USB raw-gadget + dummy_hcd reproducer is also available.

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/usb/misc/usbio.c

What this is

INTEL USBIO USB I/O EXPANDER DRIVERSMAINTAINERS section matched on drivers/usb/misc/usbio.c · Maintained

Check it on the machine

grep -wE 'CONFIG_OF|CONFIG_PCI|CONFIG_USB|CONFIG_USB_GADGET|CONFIG_USB_PHY|CONFIG_USB_SUPPORT|CONFIG_USB_USBIO' /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.

Show whether Debian builds this, per release

Debian does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.

• bookworm, trixie?
• forky, sidn

?

not established - no Makefile entry for the affected file

n

not enabled on any flavour - this release does not build the code

Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.

Build switches

CONFIG_OF, CONFIG_PCI, CONFIG_USB, CONFIG_USB_GADGET, CONFIG_USB_PHY, CONFIG_USB_SUPPORT, CONFIG_USB_USBIO

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

2026-07-25 (3 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.16%, higher than 4.9% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

drivers/usb

Upstream fixes

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

Introduced	Fixed in	Commit
6.18	6.18.39	48394f94211c
6.18	7.1.4	fc1b546973c1
6.18	7.2	8c6314489550