# CVE-2026-90336: serial: core: clear freed pointers on uart_register_driver() failure

> A use-after-free vulnerability in the Linux kernel serial core allows local attackers to potentially execute code or escalate privileges via failed driver registration.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102156, BELL-CVE-2026-90336, DEBIAN-CVE-2026-90336, GHSA-wphw-rfmf-7hpg, UBUNTU-CVE-2026-90336

## What is CVE-2026-90336?

CVE-2026-90336 is an use after free vulnerability in Linux, published on 17 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:

serial: core: clear freed pointers on uart_register_driver() failure

uart_register_driver() leaves drv->state pointing to freed memory when
tty_alloc_driver() fails. If tty_register_driver() fails, drv->tty_driver
also retains a pointer after its reference is dropped.

Drivers that use drv->state as an "already registered" flag can then skip
registration on the next probe and pass the freed state to
uart_add_one_port().

This issue was found with failslab on QEMU's raspi1ap board by
failing registration and binding the PL011 port again.

Clear both pointers on their failure paths, as uart_unregister_driver()
already does.

## Which versions are affected by CVE-2026-90336?


## How do I fix CVE-2026-90336?

Apply the vendor's patch.

## Is CVE-2026-90336 being exploited?

There is no known exploitation of CVE-2026-90336 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90336 and fix it if it is affected.

What it is: CVE-2026-90336 is an use after free vulnerability in Linux, published on 17 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-2026-90336 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-2026-90336/ (Markdown: https://insights.sbomify.com/CVE-2026-90336/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90336
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90336
- OSV: https://osv.dev/vulnerability/CVE-2026-90336

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90336/
Summaries are generated and may contain mistakes; the official description above is the record.