# CVE-2026-98749: tty: serial: max3100: shut down timer before freeing port

> A use-after-free vulnerability in the Linux kernel max3100 serial driver allows local attackers to cause a denial of service or potentially execute code via timer race conditions.

- **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:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108788, BELL-CVE-2026-98749, DEBIAN-CVE-2026-98749, GHSA-ghhr-fv6h-x88w, UBUNTU-CVE-2026-98749

## What is CVE-2026-98749?

CVE-2026-98749 is an use after free vulnerability in Linux, published on 18 Oct 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:

tty: serial: max3100: shut down timer before freeing port

max3100_shutdown() stops the polling timer but returns early during
system suspend. If the SPI device is unbound before resume, the serial
core does not call max3100_shutdown() again, so max3100_remove() frees
the port while the timer remains armed. max3100_timeout() may then
access the freed port and re-arm the timer.

Add final timer teardown to max3100_remove() and use
timer_shutdown_sync() to prevent a racing callback from re-arming it.
Also free the IRQ and destroy the workqueue there before freeing the
port. Keep timer_delete_sync() in max3100_shutdown() so that a
subsequent open() can re-arm the timer.

The workqueue is created before request_irq() and destroyed on both
request_irq() failure and normal shutdown. Its presence at remove thus
identifies the IRQ left registered when suspend bypasses shutdown.

Free the IRQ before destroying the workqueue, in both
max3100_shutdown() and max3100_remove(), and cancel the pending work
in between. free_irq() waits for a running interrupt handler to
finish and no new handler can start afterwards, so a racing handler
cannot queue work on a workqueue that is being destroyed; the
force_end_work check in max3100_dowork() only narrows that window, as
a handler delayed between the check and queue_work() could still run
after the teardown has cleared the workqueue pointer. Cancelling the
work also keeps destroy_workqueue() from waiting on a queued work item
in case remove() ever runs while the freezable workqueue is still
frozen, e.g. device removal during the resume window, before
workqueues are thawed.

This issue was found by an in-house static analysis tool.

## Which versions are affected by CVE-2026-98749?


## How do I fix CVE-2026-98749?

Apply the vendor's patch.

## Is CVE-2026-98749 being exploited?

There is no known exploitation of CVE-2026-98749 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98749 and fix it if it is affected.

What it is: CVE-2026-98749 is an use after free vulnerability in Linux, published on 18 Oct 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-2026-98749 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-2026-98749/ (Markdown: https://insights.sbomify.com/CVE-2026-98749/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98749
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98749
- OSV: https://osv.dev/vulnerability/CVE-2026-98749

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98749/
Summaries are generated and may contain mistakes; the official description above is the record.