CVE-2026-72073

What the bug is

The vub300 driver lifetime-manages its controller state using vub300->kref, with vub300_delete() freeing the mmc host when the last reference is dropped. The probe error path after the inactivity timer has been armed still bypasses that lifetime rule, however, and falls through to mmc_free_host() directly if mmc_add_host() fails. The race window is between arming the inactivity timer and reaching the probe error unwind after mmc_add_host() fails: probe thread timer/workqueue ------------ --------------- kref_init(&vub300->kref) ref = 1 kref_get(&vub300->kref) ref = 2, timer ref add_timer(inactivity_timer) fires after one second | | race window |<----------------------------------------------------> | mmc_add_host(mmc) inactivity timer fires vub300_queue_dead_work() kref_get() ref = 3 queue_work(deadwork) mmc_add_host() fails timer_delete_sync() mmc_free_host(mmc) frees vub300 deadwork runs use-after-free The inactivity timeout is one second, so this would require mmc_add_host() to both fail and take more than one second to do so. This is unlikely to happen in practice, but the error path is still wrong. timer_delete_sync() only waits for the timer callback itself. It does not flush deadwork that the callback may already have queued. As a result, queued deadwork can still hold a kref while the probe error path directly frees the backing mmc host, including the vub300 storage. Fix this by using the same lifetime mechanism as disconnect. Clear vub300->interface so that the timer callback and any queued deadwork return early and drop their references, then drop the initial probe reference and return without falling through to err_free_host.

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/mmc/host/vub300.c

What this is

VUB300 USB to SDIO/SD/MMC bridge chipMAINTAINERS section matched on drivers/mmc/host/vub300.c · linux-mmc@vger.kernel.org · Orphan

Kernel module

vub300

Check it on the machine

grep -w CONFIG_MMC_VUB300 /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 vub300

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/cloud-amd64, arm64/cloud-arm64
• trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
• forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, loong64/loong64, s390x/s390x

M

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

Build switch

CONFIG_MMC_VUB300

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

2026-08-15 (2 months 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/mmc

Upstream fixes

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

Introduced	Fixed in	Commit
6.2	6.18.42	5b82af744e06
6.2	7.1.5	618cf6b13950
6.2	7.2	a3b5f242997a
4.9.337	0	0
4.14.303	0	0
4.19.270	0	0
5.4.229	0	0
5.10.163	0	0
5.15.86	0	0
6.0.16	0	0
6.1.2	0	0