# CVE-2026-74654: serial: 8250_dma: Clear stale RX state on shutdown

> A null pointer dereference in the Linux kernel serial driver causes a kernel Oops when reopening a port with stale DMA state, leading to denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 22 Aug 2026
- **Also known as:** AZL-97346, BELL-CVE-2026-74654, DEBIAN-CVE-2026-74654, GHSA-m9j6-hfqp-5v8v, UBUNTU-CVE-2026-74654

## What is CVE-2026-74654?

CVE-2026-74654 is a vulnerability in Linux, published on 22 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:

serial: 8250_dma: Clear stale RX state on shutdown

serial8250_release_dma() terminates RX DMA and releases the channel, but
leaves rx_running set.  If the port is closed while an RX transfer is
active, the stale state remains while rxchan is NULL until the channel is
requested again on the next open.

The DesignWare BUSY workaround added by commit a7b9ce39fbe4
("serial: 8250_dw: Ensure BUSY is deasserted") calls
serial8250_rx_dma_flush() from the LCR write path during startup.  This
happens before serial8250_request_dma() obtains a new RX channel.  On
reopen, the stale rx_running state therefore makes the flush path pass a
NULL channel to dmaengine_pause(), causing a kernel Oops.

Clear rx_running after terminating RX DMA, matching the TX cleanup.  Also
make the flush helper return if the DMA object or RX channel is not
available so startup and teardown paths cannot pass a NULL channel to the
DMAengine API.

## Which versions are affected by CVE-2026-74654?


## How do I fix CVE-2026-74654?

Apply the vendor's patch.

## Is CVE-2026-74654 being exploited?

There is no known exploitation of CVE-2026-74654 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74654 and fix it if it is affected.

What it is: CVE-2026-74654 is a vulnerability in Linux, published on 22 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-2026-74654 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-2026-74654/ (Markdown: https://insights.sbomify.com/CVE-2026-74654/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74654
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74654
- OSV: https://osv.dev/vulnerability/CVE-2026-74654

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74654/
Summaries are generated and may contain mistakes; the official description above is the record.