CVE-2026-72073 mmc: vub300: fix use-after-free on probe failure
A use-after-free vulnerability in the Linux kernel vub300 MMC driver allows local attackers to potentially execute code or cause a denial of service via a race condition during probe failure.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72073?
CVE-2026-72073 is an use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mmc: vub300: fix use-after-free on probe failure
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.
Which versions are affected by CVE-2026-72073?
How do I fix CVE-2026-72073?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-72073 being exploited?
There is no known exploitation of CVE-2026-72073 in the wild and no public exploit code.
Sources
Also known as AZL-96525, BELL-CVE-2026-72073, DEBIAN-CVE-2026-72073, GHSA-2w4f-22fv-v9w4, UBUNTU-CVE-2026-72073.