# 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.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** AZL-97700, BELL-CVE-2026-80556, DEBIAN-CVE-2026-80556, GHSA-4ppc-mf9q-3j92, UBUNTU-CVE-2026-80556

## 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.

## Is CVE-2026-80556 being exploited?

There is no known exploitation of CVE-2026-80556 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80556 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-80556 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80556/ (Markdown: https://insights.sbomify.com/CVE-2026-80556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80556
- OSV: https://osv.dev/vulnerability/CVE-2026-80556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80556/
Summaries are generated and may contain mistakes; the official description above is the record.