CVE-2026-80556 mmc: atmel-mci: Fix use-after-free in atmci_remove due to race condition
A race condition in the Atmel MMC driver allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80556?
CVE-2026-80556 is a high-severity use after free vulnerability in Linux, published on 26 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: atmel-mci: Fix use-after-free in atmci_remove due to race condition
In atmci_probe, &host->bh_work is bound with atmci_work_func, and atmci_interrupt, atmci_timeout_timer and atmci_dma_complete can all queue this work on system_bh_wq.
If we remove the module, atmci_remove makes cleanup and the memory allocated for host with devm_kzalloc() is released after the remove callback returns, while the work mentioned above may still be pending or running. The sequence of operations that may lead to a UAF bug is as follows:
CPU0 CPU1
| atmci_interrupt | queue_work(system_bh_wq, | &host->bh_work) atmci_remove | atmci_cleanup_slot(...) | atmci_writel(host, ATMCI_IDR, ~0UL) | timer_delete_sync(&host->timer) | dma_release_channel(host->dma.chan) | free_irq(platform_get_irq(pdev, 0), host) | | atmci_work_func | // use host // devm resources released after | // remove returns, host is freed | | // use host (use-after-free)
Fix it by canceling the work after all the sources that can schedule it (IRQ handler, timeout timer and DMA completion callback) have been stopped, and before proceeding with the remaining cleanup in atmci_remove.
Which versions are affected by CVE-2026-80556?
How do I fix CVE-2026-80556?
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-2026-80556 being exploited?
There is no known exploitation of CVE-2026-80556 in the wild and no public exploit code.
Sources
Also known as AZL-97700, BELL-CVE-2026-80556, DEBIAN-CVE-2026-80556, GHSA-4ppc-mf9q-3j92, UBUNTU-CVE-2026-80556.