# CVE-2026-43203: atm: fore200e: fix use-after-free in tasklets during device removal

> A use-after-free vulnerability in the Linux kernel ATM fore200e driver allows attackers to execute arbitrary code or escalate privileges during device removal.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-43203, DEBIAN-CVE-2026-43203, GHSA-864f-qffm-34wc, ROOT-OS-DEBIAN-11-CVE-2026-43203, ROOT-OS-UBUNTU-2204-CVE-2026-43203, ROOT-OS-UBUNTU-2404-CVE-2026-43203, UBUNTU-CVE-2026-43203

## What is CVE-2026-43203?

CVE-2026-43203 is a high-severity use after free vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

atm: fore200e: fix use-after-free in tasklets during device removal

When the PCA-200E or SBA-200E adapter is being detached, the fore200e
is deallocated. However, the tx_tasklet or rx_tasklet may still be running
or pending, leading to use-after-free bug when the already freed fore200e
is accessed again in fore200e_tx_tasklet() or fore200e_rx_tasklet().

One of the race conditions can occur as follows:

CPU 0 (cleanup)           | CPU 1 (tasklet)
fore200e_pca_remove_one() | fore200e_interrupt()
  fore200e_shutdown()     |   tasklet_schedule()
    kfree(fore200e)       | fore200e_tx_tasklet()
                          |   fore200e-> // UAF

Fix this by ensuring tx_tasklet or rx_tasklet is properly canceled before
the fore200e is released. Add tasklet_kill() in fore200e_shutdown() to
synchronize with any pending or running tasklets. Moreover, since
fore200e_reset() could prevent further interrupts or data transfers,
the tasklet_kill() should be placed after fore200e_reset() to prevent
the tasklet from being rescheduled in fore200e_interrupt(). Finally,
it only needs to do tasklet_kill() when the fore200e state is greater
than or equal to FORE200E_STATE_IRQ, since tasklets are uninitialized
in earlier states. In a word, the tasklet_kill() should be placed in
the FORE200E_STATE_IRQ branch within the switch...case structure.

This bug was identified through static analysis.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-43203?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43203?

Apply the vendor's patch.

## Is CVE-2026-43203 being exploited?

There is no known exploitation of CVE-2026-43203 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43203 and fix it if it is affected.

What it is: CVE-2026-43203 is a high-severity use after free vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-43203 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43203/ (Markdown: https://insights.sbomify.com/CVE-2026-43203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43203
- OSV: https://osv.dev/vulnerability/CVE-2026-43203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43203/
Summaries are generated and may contain mistakes; the official description above is the record.