# CVE-2026-98239: net: lan743x: fix RX checksum use-after-free

> A use-after-free vulnerability in the LAN743x network driver allows attackers to cause memory corruption or system crashes via crafted multi-buffer packets.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106275, BELL-CVE-2026-98239, DEBIAN-CVE-2026-98239, GHSA-qcgj-xcvr-2727, UBUNTU-CVE-2026-98239

## What is CVE-2026-98239?

CVE-2026-98239 is a high-severity use after free vulnerability in Linux, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net: lan743x: fix RX checksum use-after-free

lan743x_rx_process_buffer() adds each non-first receive buffer to the
head skb's frag_list.  On the last descriptor, lan743x_rx_trim_skb()
linearizes the head and frees the fragment skb metadata.

The checksum-success path then writes ip_summed through the local skb
pointer, which still points to the final fragment.  This causes a
use-after-free write when a packet spans more than one receive buffer.

Set ip_summed on the surviving head skb instead.  Multi-buffer receive
can occur after a live MTU increase because existing ring entries keep
their old buffer size until they are replenished.

A KUnit test invoking lan743x_rx_process_buffer() with a two-buffer
packet produced a one-byte KASAN use-after-free write before this change.
The same test passed after the change.  The driver object also builds
with W=1.  This was not tested on physical LAN743x hardware.

## Which versions are affected by CVE-2026-98239?


## How do I fix CVE-2026-98239?

Apply the vendor's patch.

## Is CVE-2026-98239 being exploited?

There is no known exploitation of CVE-2026-98239 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98239 and fix it if it is affected.

What it is: CVE-2026-98239 is a high-severity use after free vulnerability in Linux, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98239 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-2026-98239/ (Markdown: https://insights.sbomify.com/CVE-2026-98239/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98239
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98239
- OSV: https://osv.dev/vulnerability/CVE-2026-98239

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98239/
Summaries are generated and may contain mistakes; the official description above is the record.