# CVE-2026-89440: mmc: via-sdmmc: stop card-detect handling on probe failure

> A use-after-free vulnerability in the Linux kernel's via-sdmmc driver allows attackers to cause denial of service or execute code via improper interrupt handling on probe failure.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100836, BELL-CVE-2026-89440, DEBIAN-CVE-2026-89440, GHSA-g7ff-3gj4-4wp3, UBUNTU-CVE-2026-89440

## What is CVE-2026-89440?

CVE-2026-89440 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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: via-sdmmc: stop card-detect handling on probe failure

request_irq() registers the SD card-detect interrupt and the probe enables
it before mmc_add_host() runs. If mmc_add_host() fails, the error path only
unmaps the registers and returns: the interrupt stays registered, so the
handler keeps running against the host once it is freed. via_sdc_isr()
dereferences sdhost and its MMIO base and schedules carddet_work, which
via_sdc_card_detect() also runs against freed memory through its
container_of() dereference.

Add a probe-error path that disables and frees the interrupt and cancels
carddet_work before unmapping. carddet_work can re-enable the device
interrupt via via_reset_pcictrl(), which restores PCIINTCTRL, so mask it
again after cancelling the work.

This issue was found by an in-house static analysis tool and confirmed by
manual code review.

## Which versions are affected by CVE-2026-89440?


## How do I fix CVE-2026-89440?

Apply the vendor's patch.

## Is CVE-2026-89440 being exploited?

There is no known exploitation of CVE-2026-89440 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89440 and fix it if it is affected.

What it is: CVE-2026-89440 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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-2026-89440 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-2026-89440/ (Markdown: https://insights.sbomify.com/CVE-2026-89440/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89440
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89440
- OSV: https://osv.dev/vulnerability/CVE-2026-89440

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89440/
Summaries are generated and may contain mistakes; the official description above is the record.