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CVE-2026-63927

usb: dwc2: Fix use after free in debug code

7.8 EPSS 0.2% AV:L

Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/usb. Debian urgency: not yet assigned.

What to do, per Debian release

Debian's own status for CVE-2026-63927 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source

Release	Status	Version	What this means
Debian 12bookworm	fixed	6.1.176-1	Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts.
Debian 13trixie	fixed	6.12.94-1	Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts.
Debian 14forky	fixed	7.0.12-1	Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts.
Debian unstablesid	fixed	7.0.12-1	Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts.

The vulnerability

What the bug is

We're not allowed to dereference "urb" after calling usb_hcd_giveback_urb() so save the urb->status ahead of time.

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/dwc2/hcd.c

What this is: DESIGNWARE USB2 DRD IP DRIVERMAINTAINERS section matched on drivers/usb/dwc2/ · linux-usb@vger.kernel.org · Maintained
Kernel module: dwc2

Check it on the machine

grep -wE 'CONFIG_OF|CONFIG_PCI|CONFIG_USB|CONFIG_USB_DWC2|CONFIG_USB_GADGET|CONFIG_USB_PHY|CONFIG_USB_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 dwc2

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.

bookwormMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x

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

Build switches: CONFIG_OF, CONFIG_PCI, CONFIG_USB, CONFIG_USB_DWC2, CONFIG_USB_GADGET, CONFIG_USB_PHY, CONFIG_USB_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

Debian tracker CVE record NVD kernel CNA record

Signals

Published: 2026-07-19 (3 months ago)source
CVSS: 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it
Attack vector: local (AV:L)source
EPSS: 0.16%, higher than 5.2% of all CVEssource
CISA KEV: not listedthe KEV catalogue
Debian urgency: not yet assignedsource
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
3.10	5.10.259	d5fc183ed614
3.10	5.15.210	63b0dafa676a
3.10	6.1.176	9fe1d84f7e2c
3.10	6.6.143	0584af4fe40f
3.10	6.12.93	a15eeeceb94c
3.10	6.18.35	84ea928ed584
3.10	7.0.12	6d0b79d1d111
3.10	7.1	9ea06a3fbf9f

Why the CNA scored it this way

Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source

AV:LAttack vector, local: The vulnerable dwc2 HCD urb_dequeue path is reached from local usbfs ioctls (USBDEVFS_SUBMITURB/DISCARDURB) on /dev/bus/usb device nodes, as well as from kernel unlink paths during USB I/O cancellation on dwc2-equipped embedded systems, kiosks, and mobile OTG hosts.
AC:LAttack complexity, low: Once debug is enabled, an attacker can reliably drive the path by submitting and cancelling URBs (or forcing disconnect/error unlink storms) and can control the HCD_BH giveback race by running concurrent cancellation requests.
PR:LPrivileges required, low: Triggering urb dequeue via usbfs requires only local user access to a USB device node (typically root or plugdev-group membership), which is low privilege and commonly available on dwc2 embedded platforms; no real root in the init namespace is required.
UI:NUser interaction, none: Exploitation requires only the attacker to submit and cancel USB transfers (or insert/disconnect a malicious USB device); no action by a separate victim user is needed.
S:UScope, unchanged: The UAF corrupts kernel heap memory within the kernel's own security authority and does not by itself cross a VM, container, or IOMMU boundary.
C:HConfidentiality impact, high: Use-after-free of a kmalloc-backed struct urb after giveback can be groomed via heap spraying to obtain arbitrary kernel memory read primitives, not merely a bounded leak.
I:HIntegrity impact, high: UAF on the URB object in the general kmalloc slab enables attacker-controlled reuse of freed memory, supporting control-flow hijack and arbitrary kernel write/code execution.
A:HAvailability impact, high: The post-giveback dereference can cause kernel oops/panic during URB teardown, and successful UAF exploitation can crash or hang the system.